WO2011085873A1 - Inductively heatable adhesive tape having differential detachment properties - Google Patents

Inductively heatable adhesive tape having differential detachment properties Download PDF

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Publication number
WO2011085873A1
WO2011085873A1 PCT/EP2010/069041 EP2010069041W WO2011085873A1 WO 2011085873 A1 WO2011085873 A1 WO 2011085873A1 EP 2010069041 W EP2010069041 W EP 2010069041W WO 2011085873 A1 WO2011085873 A1 WO 2011085873A1
Authority
WO
WIPO (PCT)
Prior art keywords
heat
adhesive
activatable
electrically conductive
activated
Prior art date
Application number
PCT/EP2010/069041
Other languages
German (de)
French (fr)
Inventor
Klaus KEITE-TELGENBÜSCHER
Hans Karl Engeldinger
Judith Grünauer
Original Assignee
Tesa Se
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tesa Se filed Critical Tesa Se
Priority to EP10790401.3A priority Critical patent/EP2516573B1/en
Priority to CN201080064430XA priority patent/CN102762682A/en
Priority to ES10790401.3T priority patent/ES2664193T3/en
Priority to US13/517,927 priority patent/US20130020022A1/en
Priority to MX2012006705A priority patent/MX344318B/en
Priority to JP2012545203A priority patent/JP2013515112A/en
Publication of WO2011085873A1 publication Critical patent/WO2011085873A1/en

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/34Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
    • B29C65/36Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction
    • B29C65/3672Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the composition of the elements heated by induction which remain in the joint
    • B29C65/3676Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the composition of the elements heated by induction which remain in the joint being metallic
    • B29C65/368Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the composition of the elements heated by induction which remain in the joint being metallic with a polymer coating
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/34Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
    • B29C65/36Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction
    • B29C65/3604Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the type of elements heated by induction which remain in the joint
    • B29C65/3608Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the type of elements heated by induction which remain in the joint comprising single particles, e.g. fillers or discontinuous fibre-reinforcements
    • B29C65/3612Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the type of elements heated by induction which remain in the joint comprising single particles, e.g. fillers or discontinuous fibre-reinforcements comprising fillers
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/48Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding
    • B29C65/50Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding using adhesive tape, e.g. thermoplastic tape; using threads or the like
    • B29C65/5007Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding using adhesive tape, e.g. thermoplastic tape; using threads or the like characterised by the structure of said adhesive tape, threads or the like
    • B29C65/5021Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding using adhesive tape, e.g. thermoplastic tape; using threads or the like characterised by the structure of said adhesive tape, threads or the like being multi-layered
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/48Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding
    • B29C65/50Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding using adhesive tape, e.g. thermoplastic tape; using threads or the like
    • B29C65/5057Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding using adhesive tape, e.g. thermoplastic tape; using threads or the like positioned between the surfaces to be joined
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/76Making non-permanent or releasable joints
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/01General aspects dealing with the joint area or with the area to be joined
    • B29C66/05Particular design of joint configurations
    • B29C66/10Particular design of joint configurations particular design of the joint cross-sections
    • B29C66/11Joint cross-sections comprising a single joint-segment, i.e. one of the parts to be joined comprising a single joint-segment in the joint cross-section
    • B29C66/112Single lapped joints
    • B29C66/1122Single lap to lap joints, i.e. overlap joints
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/40General aspects of joining substantially flat articles, e.g. plates, sheets or web-like materials; Making flat seams in tubular or hollow articles; Joining single elements to substantially flat surfaces
    • B29C66/41Joining substantially flat articles ; Making flat seams in tubular or hollow articles
    • B29C66/43Joining a relatively small portion of the surface of said articles
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/80General aspects of machine operations or constructions and parts thereof
    • B29C66/81General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps
    • B29C66/812General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the composition, by the structure, by the intensive physical properties or by the optical properties of the material constituting the pressing elements, e.g. constituting the welding jaws or clamps
    • B29C66/8122General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the composition, by the structure, by the intensive physical properties or by the optical properties of the material constituting the pressing elements, e.g. constituting the welding jaws or clamps characterised by the composition of the material constituting the pressing elements, e.g. constituting the welding jaws or clamps
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/90Measuring or controlling the joining process
    • B29C66/91Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux
    • B29C66/914Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux
    • B29C66/9141Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the temperature
    • B29C66/91411Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the temperature of the parts to be joined, e.g. the joining process taking the temperature of the parts to be joined into account
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/90Measuring or controlling the joining process
    • B29C66/91Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux
    • B29C66/914Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux
    • B29C66/9161Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the heat or the thermal flux, i.e. the heat flux
    • B29C66/91651Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the heat or the thermal flux, i.e. the heat flux by controlling or regulating the heat generated by Joule heating or induction heating
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/90Measuring or controlling the joining process
    • B29C66/91Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux
    • B29C66/919Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux characterised by specific temperature, heat or thermal flux values or ranges
    • B29C66/9192Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux characterised by specific temperature, heat or thermal flux values or ranges in explicit relation to another variable, e.g. temperature diagrams
    • B29C66/91921Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux characterised by specific temperature, heat or thermal flux values or ranges in explicit relation to another variable, e.g. temperature diagrams in explicit relation to another temperature, e.g. to the softening temperature or softening point, to the thermal degradation temperature or to the ambient temperature
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/90Measuring or controlling the joining process
    • B29C66/91Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux
    • B29C66/919Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux characterised by specific temperature, heat or thermal flux values or ranges
    • B29C66/9192Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux characterised by specific temperature, heat or thermal flux values or ranges in explicit relation to another variable, e.g. temperature diagrams
    • B29C66/91921Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux characterised by specific temperature, heat or thermal flux values or ranges in explicit relation to another variable, e.g. temperature diagrams in explicit relation to another temperature, e.g. to the softening temperature or softening point, to the thermal degradation temperature or to the ambient temperature
    • B29C66/91931Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux characterised by specific temperature, heat or thermal flux values or ranges in explicit relation to another variable, e.g. temperature diagrams in explicit relation to another temperature, e.g. to the softening temperature or softening point, to the thermal degradation temperature or to the ambient temperature in explicit relation to the fusion temperature or melting point of the material of one of the parts to be joined
    • B29C66/91935Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux characterised by specific temperature, heat or thermal flux values or ranges in explicit relation to another variable, e.g. temperature diagrams in explicit relation to another temperature, e.g. to the softening temperature or softening point, to the thermal degradation temperature or to the ambient temperature in explicit relation to the fusion temperature or melting point of the material of one of the parts to be joined lower than said fusion temperature
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J5/00Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers
    • C09J5/06Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers involving heating of the applied adhesive
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00Adhesives in the form of films or foils
    • C09J7/20Adhesives in the form of films or foils characterised by their carriers
    • C09J7/22Plastics; Metallised plastics
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00Adhesives in the form of films or foils
    • C09J7/20Adhesives in the form of films or foils characterised by their carriers
    • C09J7/28Metal sheet
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00Adhesives in the form of films or foils
    • C09J7/30Adhesives in the form of films or foils characterised by the adhesive composition
    • C09J7/35Heat-activated
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/34Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
    • B29C65/36Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction
    • B29C65/3604Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the type of elements heated by induction which remain in the joint
    • B29C65/3644Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the type of elements heated by induction which remain in the joint being a ribbon, band or strip
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/48Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding
    • B29C65/4805Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding characterised by the type of adhesives
    • B29C65/481Non-reactive adhesives, e.g. physically hardening adhesives
    • B29C65/4815Hot melt adhesives, e.g. thermoplastic adhesives
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/48Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding
    • B29C65/4805Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding characterised by the type of adhesives
    • B29C65/481Non-reactive adhesives, e.g. physically hardening adhesives
    • B29C65/4825Pressure sensitive adhesives
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/48Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding
    • B29C65/4805Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding characterised by the type of adhesives
    • B29C65/483Reactive adhesives, e.g. chemically curing adhesives
    • B29C65/4835Heat curing adhesives
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/48Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding
    • B29C65/50Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding using adhesive tape, e.g. thermoplastic tape; using threads or the like
    • B29C65/5007Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding using adhesive tape, e.g. thermoplastic tape; using threads or the like characterised by the structure of said adhesive tape, threads or the like
    • B29C65/5014Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding using adhesive tape, e.g. thermoplastic tape; using threads or the like characterised by the structure of said adhesive tape, threads or the like being fibre-reinforced
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/82Testing the joint
    • B29C65/8207Testing the joint by mechanical methods
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/82Testing the joint
    • B29C65/8207Testing the joint by mechanical methods
    • B29C65/8215Tensile tests
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/01General aspects dealing with the joint area or with the area to be joined
    • B29C66/03After-treatments in the joint area
    • B29C66/034Thermal after-treatments
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/70General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/71General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the composition of the plastics material of the parts to be joined
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/70General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/73General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset
    • B29C66/735General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the extensive physical properties of the parts to be joined
    • B29C66/7352Thickness, e.g. very thin
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/80General aspects of machine operations or constructions and parts thereof
    • B29C66/83General aspects of machine operations or constructions and parts thereof characterised by the movement of the joining or pressing tools
    • B29C66/832Reciprocating joining or pressing tools
    • B29C66/8322Joining or pressing tools reciprocating along one axis
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/90Measuring or controlling the joining process
    • B29C66/91Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux
    • B29C66/919Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux characterised by specific temperature, heat or thermal flux values or ranges
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/90Measuring or controlling the joining process
    • B29C66/92Measuring or controlling the joining process by measuring or controlling the pressure, the force, the mechanical power or the displacement of the joining tools
    • B29C66/929Measuring or controlling the joining process by measuring or controlling the pressure, the force, the mechanical power or the displacement of the joining tools characterized by specific pressure, force, mechanical power or displacement values or ranges
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/90Measuring or controlling the joining process
    • B29C66/94Measuring or controlling the joining process by measuring or controlling the time
    • B29C66/949Measuring or controlling the joining process by measuring or controlling the time characterised by specific time values or ranges
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00Additional features of adhesives in the form of films or foils
    • C09J2301/10Additional features of adhesives in the form of films or foils characterized by the structural features of the adhesive tape or sheet
    • C09J2301/12Additional features of adhesives in the form of films or foils characterized by the structural features of the adhesive tape or sheet by the arrangement of layers
    • C09J2301/124Additional features of adhesives in the form of films or foils characterized by the structural features of the adhesive tape or sheet by the arrangement of layers the adhesive layer being present on both sides of the carrier, e.g. double-sided adhesive tape
    • C09J2301/1242Additional features of adhesives in the form of films or foils characterized by the structural features of the adhesive tape or sheet by the arrangement of layers the adhesive layer being present on both sides of the carrier, e.g. double-sided adhesive tape the opposite adhesive layers being different
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00Additional features of adhesives in the form of films or foils
    • C09J2301/30Additional features of adhesives in the form of films or foils characterized by the chemical, physicochemical or physical properties of the adhesive or the carrier
    • C09J2301/304Additional features of adhesives in the form of films or foils characterized by the chemical, physicochemical or physical properties of the adhesive or the carrier the adhesive being heat-activatable, i.e. not tacky at temperatures inferior to 30°C
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00Additional features of adhesives in the form of films or foils
    • C09J2301/50Additional features of adhesives in the form of films or foils characterized by process specific features
    • C09J2301/502Additional features of adhesives in the form of films or foils characterized by process specific features process for debonding adherents
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2400/00Presence of inorganic and organic materials
    • C09J2400/10Presence of inorganic materials
    • C09J2400/16Metal
    • C09J2400/163Metal in the substrate
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/24Structurally defined web or sheet [e.g., overall dimension, etc.]
    • Y10T428/24942Structurally defined web or sheet [e.g., overall dimension, etc.] including components having same physical characteristic in differing degree

Definitions

  • the invention relates to a method for bonding two substrates, in particular two plastic substrates, to each other by means of heat-activating adhesives, and furthermore to a method for re-dissolving the bonding composite of the substrate which has been produced in this way.
  • Heat-activated, bondable surface elements are used to obtain high-strength joints of parts to be joined.
  • such surface elements are suitable to achieve comparable or higher strengths at a smaller thickness of the adhesive joint than is possible with surface elements which contain exclusively PSA systems.
  • Such high strength bonds are particularly important in the advancing miniaturization of electronic devices, such as consumer electronics, consumer electronics, or communications electronics, for example, cell phones, PDAs, laptops and other computers, digital cameras, and display devices such as displays and digital readers.
  • heat-activated adhesive surface elements which have heat-activated adhesive adhesives, ie adhesives which have no or at most low Eigenklebrtechnik at room temperature, under the action of heat but the adhesive force required for bonding to the respective Build bonding substrates (joining partners, primer).
  • heat-activated adhesive adhesives are often present in solid form at room temperature, but are transferred to a state of high bond strength either reversibly or irreversibly during bonding by the action of temperature.
  • Reversibly heat-activated adhesive adhesives are, for example, adhesives based on thermoplastic polymers, whereas adhesives that are irreversibly heat-activated are reactive adhesives in which, as a result of thermal activation, chemical reactions such as crosslinking occur, whereby these adhesives are particularly suitable for permanent high-strength adhesions.
  • heat-activatable adhesive tapes In order to adapt heat-activatable adhesive tapes to two joining partners made of different materials, for example of metal and plastic, it is known in the prior art to use a multi-layered adhesive tape containing different heat-activatable adhesives on each side (see, for example, DE 10 2006 055 093 A1 ). Such multilayer heat-activatable adhesive tapes are also used in areas in which pressure-sensitive adhesive properties are to be introduced into heat-activatable adhesive tapes, for example in order to hold the joining parts in position.
  • At least one layer is at least partially designed as a pressure-sensitive adhesive, which in special cases can also be converted into a non-tacky state by a chemical reaction-which as a rule is heat-activated (cf., for example, EP 1 078 965 A2 and US Pat. No. 4,120,712) A)
  • stampings adapted from adhesive tapes to the geometry of the glue joint.
  • internal plastic films are proposed, which are each provided with a heat-activatable adhesive on each side, which may also be different.
  • All heat-activated bonding adhesive systems have in common that they must be heated during bonding. Particularly in the case of adhesions in which the adhesive composition systems are covered over the entire surface of the bonding substrates to the outside, it is particularly important to quickly transport the heat required for melting or activation of the adhesive to the bonding surface. If one of the bonding substrates is a good heat conductor, it is possible to heat this bonding substrate by an external heat source, for example by a direct heat exchanger, an infrared heater or the like. However, in the case of such direct heating or contact heating, the short heating time required for rapid, homogeneous heating of the known adhesive can only be realized for a large temperature gradient between the heat source and the bonding substrate.
  • the bonding substrate to be heated itself should be insensitive to temperatures which may in some cases even be significantly higher than would actually require the melting or activation of the adhesive.
  • the problem is therefore the use of heat-activated adhesive films for plastic-plastic bonds.
  • plastics for example, in the consumer goods electronics, for example, polyvinyl chloride (PVC), acrylonitrile-butadiene-styrene copolymers (ABS), polycarbonates (PC), polypropylene (PP) or blends based on these plastics are used.
  • the situation is different if none of the bonding substrates conducts the heat sufficiently well or if the bonding substrates are sensitive to higher temperatures, as is the case for many plastics, but also electronic components such as semiconductor devices or liquid crystal modules.
  • the heat-activated glued surface element itself with an intrinsic mechanism for heating, so that the heat required for bonding need not be introduced from the outside, but directly inside the surface element itself is generated.
  • Various mechanisms are known from the prior art, by means of which such an internal heating can be realized, such as heating by means of an electrical resistance heating, by magnetic induction or as a result of an interaction with microwave radiation.
  • the heating in the alternating magnetic field is on the one hand by induced eddy currents in electrically conductive receptors, on the other - model - explained - achieved by hysteresis losses of the umklappenden elementary magnets in the alternating field.
  • a minimum size of the conductive domains is required. This minimum size increases the lower the frequency of the alternating field.
  • both effects occur together (e.g., magnetic metals) or only one effect at a time (e.g., aluminum: eddy only, iron oxide particles: hyteresis only).
  • various heating devices for inductive heating are known; These can be distinguished among other things according to the frequencies that has the magnetic alternating field generated by the respective heating device.
  • an induction heating can be done using a magnetic field whose frequency in the Frequency range from about 100 Hz to about 200 kHz (the so-called center frequencies, MF) or in the frequency range from about 300 kHz to about 100 MHz (the so-called high frequencies, HF).
  • heating devices are known whose magnetic field has a frequency from the range of microwaves, for example, the microwave standard frequency of 2.45 GHz.
  • induction heating manufacturing processes from the fields of gluing, seam sealing, hardening, tempering and the like can serve.
  • the common technique is to use such methods in which the inductors comprise components completely or partially and uniformly over the entire circumference or intentionally unevenly heat when needed, eg. Example, according to EP 1 056 312 A2 or DE 20 2007 003 450 U1.
  • a method for fusing a container opening with a sealing film in which the metallic insert of a sealing film is heated by induction and by heat conduction a sealant is melted.
  • the containers are closed by a screw-on or latchable lid, which contains a metal foil and a plastic sealing film arranged adjacently.
  • the induction coil With the help of the induction coil eddy currents are generated in the metal foil, which heat the metal foil. Due to the contact between the metal foil and the sealing foil, the sealing foil is also heated and thereby fused with the container opening.
  • Tunnel-shaped induction coils have the advantage over flat coils that also containers with a large distance between the metal foil and the Cover upper edge can be sealed because the coil acts from the side of the metal foil.
  • a disadvantage of this method is that a much larger part of the component volume than the pure adhesive volume and the metal foil is guided by the electromagnetic field and thus damages are not excluded in the case of an electronic component, since heating can occur at undesirable points.
  • a further disadvantage is that the entire cover sheet is heated, with only the edge area in contact with the container being sufficient for the bonding. This results in a large ratio of heated area to bonding area, which is about 6.5 for typical beverage bottles with an opening diameter of 25 mm and a bond width of 2 mm. For larger container diameter with usually constant bond width increases the ratio.
  • inductively heatable heat-activatable adhesive films which can be inductively heat-activated adhesive foils (HAFs)
  • HAFs inductively heat-activated adhesive foils
  • heat-activatable films which are to be heated inductively, may be filled with metallic or metallized sheets. This is also very efficient in the middle frequency range when using full-surface metal foils, high heating rates can be achieved, so that induction times between 0.05 and 10 s can be realized. It is also the use of very thin conductive films between 0.25 ⁇ and 75 ⁇ possible.
  • the product Duolplocoll RCD from Lohmann equipped with inductively heatable nanoparticles is known. This can only be used technically in the high-frequency range to heat.
  • the above-described disadvantages of the use of particles and high-frequency alternating fields also apply to this product.
  • the possibility of solving adhesive bonds produced by means of re-inductive heating is also presented.
  • a disadvantage of such particle-filled adhesive tapes is that at high heating, the cohesion subsides and thus after separation of the components are adhesive tape residues on both joining partners, which are each contaminated with particles. This is unfavorable for material recycling.
  • Object of the present invention was to provide a material and methods available, with the bonding, in particular plastic-plastic bonds under Avoiding the disadvantages of the prior art produced and controlled again can be separated.
  • the object is achieved by a method for bonding (so that an adhesive bond is formed) and redissolving (so that the adhesive bond is separated again) of two substrate surfaces, wherein for bonding a heat-activated glued surface element is used, the heat-activated glued surface element at least one electrically conductive sheet and at least two layers of different heat-activatable adhesives, wherein the first heat-activatable adhesive layer is substantially on one side of the electrically conductive sheet and the second heat-activatable adhesive is substantially on the other side of the electrically conductive sheet, characterized in that
  • the bonding is effected by subjecting the heat-activated, bondable surface element to a first temperature (T-i) at which a simultaneous heat activation of the two heat-activatable adhesives takes place,
  • the redissolution is effected by the bonding point (ie in particular the heat-activated bonded surface element) being exposed to a second temperature (T 2 ) under which only one of the heat-activatable layers (hereinafter - merely for language distinction) is designated as the first heat-activatable layer Adhesive "referred to) of the heat-activated surface element loses its adhesive effect in the adhesive bond as far as the adhesive bond is separated.
  • the term “heat-activated adhesive surface element” in the corresponding cases also includes “heat-activated bonded surface elements", unless otherwise described.
  • a “heat-activated adhesive surface element” and the heat-activatable adhesives to such adhesives that can form the suitability for bonding in the sense of application by reaching an activation temperature above room temperature.
  • the heat-activatable adhesive is essentially located on one side of the sheet
  • the adhesive on the respective surface element side causes the bonding completely or for the most part, but in concrete tape construction on the other side of the electrically conductive Sheet may extend, for example, by overlapping the sheet edges, by flowing into each other with the opposite heat-activatable adhesive, for example, in interrupted electrically conductive sheets, such as gratings, perforated plates and the like, or otherwise, at least insofar as that the realization
  • the inventive concept is therefore not influenced by this "essentially” takes into account the fact that the respective heat-activatable adhesive can be completely on the respective side of the electrically conductive fabric, but not mu ss, as far as it is ensured that the bonding of the heat-activated bondable surface element on the respective substrate is significantly ensured by the respective heat-activatable adhesive significantly.
  • the surface element in the context of this application, in particular all conventional and suitable structures apply with substantially sheet-like extent. These allow a surface bonding and can be configured differently, in particular flexible, as an adhesive film, adhesive tape, adhesive label or as Formstanzling.
  • the surface element may be formed as a cut surface element whose shape is adapted to the shape of the bonding surface in order to reduce the risk that the bonding substrate is thermally damaged in the course of inductive heating.
  • the terms front and back refer to the two surfaces of the surface element parallel to its main extent (surface extent, main extension plane) and serve only to distinguish these two arranged on opposite sides of the surface element surfaces, without that by the choice of terms, the absolute spatial arrangement of both surfaces is set; Consequently, the front side can also represent the spatially rearward side surface of the surface element, namely, accordingly, when the back side forms its spatially front side surface.
  • This heat-activated adhesive surface element is intended to glue two bonding substrates together.
  • Heat-activated adhesives that can be bonded are all adhesives which are hot-bonded at elevated temperatures and, after cooling, provide a mechanically strong bond.
  • the adhesive is in the form of an adhesive layer.
  • the term "layer” refers in particular to a planar arrangement of a system of uniform functionality whose dimensions are significantly smaller in one spatial direction (thickness or height) than in the other two spatial directions defining the main extent (length and width). Such a layer can be made compact or perforated and consist of a single material or of different materials, in particular if they contribute to the uniform functionality of this layer.
  • a layer may have a constant thickness over its entire areal extent or different thicknesses.
  • a layer may also have more than one functionality.
  • heat-activatable adhesive (also referred to in the literature as “heat-activatable adhesive”) denotes adhesives which are activated by the supply of thermal energy and applied in this state for use. By cooling, the bonding is effected, which is to distinguish between two systems: Thermoplastic heat-activated systems (hot melt adhesives) physically bind on cooling (usually reversible), while heat-reactive elastomer / reactive component systems (heat sealing adhesives) chemically set (usually irreversible ).
  • Thermoplastic heat-activated systems hot melt adhesives
  • heat-reactive elastomer / reactive component systems heat sealing adhesives
  • heat-activatable adhesive does not preclude the fact that the corresponding adhesive can already have a certain inherent tack (tack, tackiness) even at room temperature or at temperatures below the activation temperature (can be "tacky”). However, this self-tackiness below the activation temperature is not necessary, so that heat-activatable adhesive compositions can also be non-sticky at temperatures below the activation temperature, in particular at room temperature.
  • heat-activatable adhesives in the context of this document, in particular such heat-activatable adhesives are understood, which behave such that at a temperature T DK 1 ⁇ T 2 - starting from the bonded state - one of heat-activatable adhesives (the first heat-activatable adhesive) their adhesive effect loses their adhesive effect in the adhesive composite so far that the adhesive bond is separated with respect to the adhesive bond by means of this heat-activable adhesive, while the means of the other heat-activated adhesive (hereinafter referred to as "second heat-activatable adhesive") caused bonding at the temperature T 2 is maintained.
  • first heat-activatable adhesive the means of the other heat-activated adhesive
  • the second heat-activatable adhesive can advantageously be selected such that it in turn dissolves the bond to the substrate on which it is bonded at a third temperature T 3 above the temperature T 2 .
  • the separation of the respective heat-activatable adhesive from the substrate on which it is bonded for example, take place in that the respective adhesive at this temperature (T 2 or T 3 ) loses its adhesive forces or at least greatly lost by melting, softened and / or decomposes (decomposition). Further mechanisms of the separation process are possible and included in the basic idea of the invention.
  • the temperature T-i within the heat activated bonded surface elements is generated such that the electrically conductive sheet is heated inductively within the heat activated surface element, in particular in a magnetic field, and passes the heat to the adhesives.
  • the temperature T 2 preferably also the temperature T 3 to be achieved if appropriate, is caused by inductive heating of the electrically conductive sheet.
  • heat-activated gluing surface elements are advantageously used, as they are explained in more detail below and how they themselves are the subject of the invention.
  • the invention further provides a heat activated glued surface element is used, the heat activated bonded surface element comprises at least one electrically conductive sheet and at least two layers of different heat-activatable adhesives, wherein the first heat-activatable adhesive layer substantially on one side of the electrically conductive sheet and the second heat-activated Adhesive composition is substantially on the other side of the electrically conductive sheet, wherein the heat-activatable adhesives are chosen such that they cause bonding at a common temperature ⁇ , and that at a temperature T DK 1 one of the heat-activatable adhesives (the first heat-activatable adhesive) their adhesive effect loses, the other (the second heat-activatable adhesive) but not yet.
  • the heat-activated bondable surface element can be designed as desired.
  • the surface element may contain further layers, for example permanent or temporary carriers.
  • the activation energies of the first heat-activatable adhesive (T Ak t 1 ) and the second adhesive (T Ak t 2 ) are the same or differ so little that both lie in a temperature range in which upon reaching especially after exceeding the higher of the two activating energies, both heat-activatable adhesives develop their stickiness or have already unfolded, however, without the adhesive having the lower activation energy already losing its stickiness again (eg because it would become too liquid, decomposed or on another way would no longer be able to achieve the required adhesive effect (ie that the adhesive loss temperature T DK of one or both adhesives would have already been reached).
  • the first heat-activatable adhesive having the lower adhesive loss temperature T DK 1 may be the one with the lower but also the one with the higher activation temperature, provided that T Ak 1 and T Ak 2 differ. The same applies to the second heat-activatable adhesive with the higher adhesive loss temperature T DK 2 or without adhesive loss temperature.
  • the temperature Ti is chosen in particular such that it corresponds to the higher of the two activation energies or-above all-above this, so that both pressure-sensitive adhesives develop their stickiness without exceeding a temperature at which one or both - The adhesives would lose their stickiness again.
  • the temperatures at which the heat-activatable adhesives lose their stickiness (can no longer achieve the retention of the adhesive bond; adhesive loss temperatures T DK 1 of the first heat-activatable adhesive, T DK 2 of the second heat-activable adhesive) preferably differ so significantly that in terms of process technology a temperature T 2 (or a temperature range T 2 ) can be realized that the bonding of the first substrate with the first heat-activatable adhesive having the lower adhesive loss temperature T DK 1 is solved, while the bonding of the second substrate with the second heat-activatable adhesive with the higher (or without existing) adhesive loss temperature T DK 2 (still) is maintained.
  • T Akt 2 , T DK 1 and / or T DK 2 can be sharply defined temperatures, since adhesive adhesives are polymers in which phase transformations or other physical, chemical and / or physicochemical processes take place within temperature ranges Temperature ranges to be included.
  • the specified temperature T then designates in particular the temperature within the respective temperature range at which the corresponding process (heat activation, melting, softening, decomposition, etc.) has essentially taken place, so that the described success in the process (ie the bonding or the redissolving) entry.
  • the process temperature Ti denotes a temperature equal to or above the activation temperatures T A kt 1 and T Ak 2 of the heat-activatable adhesives.
  • the process temperature T 2 denotes a temperature equal to or above the adhesive loss temperature T DK 1 of the first heat-activatable adhesive; If the second heat-activatable adhesive also has an adhesive loss temperature T DK 2 , T 2 is T DK 2 .
  • the process temperature T 3 designates a temperature equal to or above the adhesive loss temperature T DK 2 * .
  • the heat-activatable adhesives having adhesive loss temperatures, independently of the respective other heat-activatable adhesive are in particular their respective melting temperature, softening temperature, decomposition temperature or the like; Of course, the adhesion loss of both heat-activatable adhesives can also be due to the same effect.
  • An advantageous embodiment of the adhesive tapes according to the invention relates to a heat-activated adhesive surface element comprising at least one electrically conductive sheet and at least one layer of heat-activatable adhesives on the two sides of the electrically conductive sheet, wherein the two heat-sensitive adhesives differ, and wherein the activation temperatures to achieve Adhesive properties of the heat-activatable adhesives differ less than their adhesive loss temperatures, in particular as their melting temperatures and / or as their decomposition temperatures.
  • the heat-activated bondable surface elements according to the invention and the method according to the invention are particularly suitable for bonding between at least two identical or different electrically non-conductive materials (substrates in the sense of the term used above), in particular those with heat conduction coefficients of less than 5 W / mK, particularly preferably in electronic Devices.
  • the bonding can be carried out in a temperature range which is the same for both in that both adhesives achieve the complete bond strength (without one of the materials not achieving its complete bond strength, for example by incomplete curing or melting).
  • both adhesives achieve the complete bond strength (without one of the materials not achieving its complete bond strength, for example by incomplete curing or melting).
  • none of the materilaien involved is damaged by excessive temperature.
  • T 2 when releasing the connection in particular a lower temperature, can also be safely predicted on which joining partner sticks the electrically conductive sheet. This is advantageous for the recycling process of the particular electronic devices, in particular for a clean material sorting.
  • the heat-activated glued surface element has a thickness of less than 70 ⁇ , in particular less than 50 ⁇ , especially of less than 30 ⁇ , as this particularly thin glued connections can be made.
  • the invention encompasses a method for producing an adhesive bond, in which a heat-activated, bondable surface element according to the invention is made available, in particular, in the geometry of the adhesive bond to be produced (for example as a blank or diecut),
  • the pressure is applied to the adhesive joint, the pressure being applied by a pressing device, of which at least one pressing tool contains a device for generating an alternating magnetic field,
  • the invention comprises a method for releasing an adhesive bond, in particular as a consequence of the previously described method for producing a bonded joint, in which an adhesive bond produced with a heat-activated adhesive surface element adhesive tape according to the invention is heated by means of induction, characterized in that
  • the heating of the surface element according to the invention can be carried out using a customary for inductive heating Indutationswekar (inductor).
  • Suitable induction heating means are all customary and suitable arrangements, that is to say coils, conductor loops or conductors through which an electric alternating current flows, which generate a magnetic alternating field of suitable strength as a result of the current flowing through it.
  • the magnetic field strength required for heating can be provided by a coil arrangement of corresponding winding number and coil length, which is traversed by a corresponding current, for example as a point inductor.
  • This may be formed without ferromagnetic core or have a core, for example, iron or pressed ferrite powder. The precombustion can be directly exposed to the magnetic field thus generated.
  • the above coil arrangement as a primary winding on the primary side of a magnetic field transformer (transformer), on whose secondary side a secondary winding provides a correspondingly higher current.
  • a magnetic field transformer transformer
  • the actual exciter coil arranged in the immediate vicinity of the preassembly can have a smaller number of turns due to the higher current, without thereby reducing the field strength of the alternating magnetic field.
  • a pressing device is additionally required for this purpose.
  • the press apparatus there may be used any apparatus suitable for applying a pressing pressure, for example, batch type press machines such as a pneumatic or hydraulic press, an eccentric press, a crank press, a toggle press, a screw press or the like, or also continuous press machines such as a press roller.
  • the device may be provided as a separate unit or connected to the inductor.
  • a device is used which, as the first pressing tool, contains at least one pressing punch element which additionally has an induction heating means.
  • the following parameters can be selected for inductive heating:
  • Frequencies of 1 to 40 kHz, in particular of 1 to 15 kHz are particularly preferably used in the method, since in this case the effective penetration depth of the magnetic field is further increased.
  • the method is used when the heated area is less than 5 cm 2 .
  • the method avoids an uncontrolled melting of the then very filigree bonding substrates.
  • the method is further used when the adhesive joint is formed as a non-closed surface.
  • These are on the one hand to be understood as recesses and / or perforated surfaces, on the other hand also substantially composed of line-shaped elements surfaces, such as a comb structure in which individual elements have an aspect ratio (length to width) of more than 2.
  • a pressing pressure is exerted on heating, which is more than 0.2 MPa.
  • heating which is more than 0.2 MPa.
  • This can be a blistering by desorbing or resulting in a chemical reaction gases, in particular by steam, avoided.
  • Preferred for high crosslinking temperatures is a pressure of more than 0.5 MPa.
  • the pressure is less than 0.2 MPa, since this squeezing of adhesive, in particular thermoplastic adhesive, can be avoided from the adhesive joint.
  • the heating rate is not more than 200 ° C / s, in particular not more than 100 ° C / s, since at higher heating rates, the risk of material damage to the heat-activated adhesive or the uncontrolled melting or thermal damage to the substrate is great.
  • Such a limitation of the heating rate may e.g. with the use of less electrically conductive metals (e.g., aluminum instead of copper or steel instead of aluminum).
  • Another technical means of limiting the heating rate is the use of openwork metallic sheets, e.g. of expanded metal).
  • the pressure is maintained after the heating of the surface element, in order to allow solidification of the adhesive joint by physical or chemical mechanisms. It is also advantageous to carry out this repressing time in a second pressing device, which no longer has to contain an inductor in order to reduce the cycle time.
  • a further induction heating of the adhesive tape is also carried out in at least part of this repressing time, since this advantageously allows the temperature in the glue joint to be maintained.
  • this reheating is carried out at a lower heating rate than the first heating.
  • the fact that the adhesive tape is preferably provided in the geometry of the bond area ensures that the heating takes place only in the areas required for the bonding. The risk of thermal damage is thus reduced.
  • the production of the geometry can be carried out by all methods familiar to the person skilled in the art, such as, for example, cutting, punching, laser cutting, water jet cutting.
  • the inductor is integrated in at least one of the pressing tools, since hereby the induction field can be brought very close to the bonding site and also spatially limited to it.
  • hot melt adhesives reactive adhesives or reactive hot melt adhesives can be used as the heat-activatable adhesives.
  • the first heat-activatable adhesive preferably has an adhesive loss temperature (T DK 1 ) of between 10 and 20 ° C., preferably between 20 and 50 ° C., more preferably at least 50 ° C. above the activation temperature (T Ak 2 * ) of the second heat-activatable adhesive lies. This ensures that both adhesives can be safely activated within a heat-up cycle without activating the release mechanism (the decomposition) for the first adhesive. With a difference of 10 - 20 ° C, the temperature necessary for disconnecting the connection is relatively low, so that heating time and / or energy can be saved.
  • T DK 1 , E Ak t 2 a difference of the above-mentioned temperatures (T DK 1 , E Ak t 2 ) of more than 50 ° C, the process is very safe, as in the temperature control during bonding larger tolerances are allowed.
  • the range of a temperature difference of 20 ° C to 50 ° C is an advantageous compromise between the two variants.
  • the first heat-activatable adhesive is or comprises a reactive adhesive or a reactive hot melt adhesive
  • the second heat-activable adhesive is or comprises a hot melt adhesive, very preferably the melting temperature of the hot melt adhesive being smaller as the decomposition temperature (decomposition temperature) of the reactive system is selected. This can be done a release of the adhesive bond without chemical decomposition (decomposition) and thus possible danger from the resulting gases or other decomposition products.
  • At least one of the heat-activatable adhesives contains fractions of at least one material which accelerate the decomposition or which preferably decompose and thus weaken the adhesive bond and lead to the solution thereof. Examples of these are known to those skilled in the art and e.g. shown in US 5,272,216. The corresponding materials shown there are explicitly included in the disclosure of the present specification.
  • thermoplastic heat-activated adhesives hot-melt adhesives
  • reactive heat-activated adhesives reactive hot melt adhesives
  • Thermoplastic adhesives are based on polymers that soften reversibly when heated and solidify again during cooling.
  • reactive heat activated adhesives contain reactive components.
  • the latter constituents are also referred to as "reactive resins” in which the heating initiates a crosslinking process which, after completion of the crosslinking reaction, ensures a permanent stable compound even under pressure.
  • Such thermoplastic adhesives preferably also contain elastic components, for example synthetic nitrile rubbers. Due to their high flow viscosity, such elastic components impart to the heat-activated adhesive composition a particularly high dimensional stability even under pressure.
  • thermoplastic heat-activated adhesive composition thus contains a thermoplastic base polymer. This has a good flow behavior even at low contact pressure, so that the for the durability of a permanent bond setting relevant final bond strength within a short contact time and therefore rapid bonding is also possible on rough or otherwise critical substrates.
  • Thermoplastic adhesives which can be adhesively bonded to form a heat-activated adhesive can be any of the thermoplastic adhesives known from the prior art.
  • Suitable examples are those heat-activatable adhesives, as described in DE 10 2006 042 816 A1, without wishing to be limited by this information.
  • thermoplastic adhesive may for example contain or even consist of one or more of the following components: polyolefins, ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, polyamides, polyesters, polyurethanes or butadiene-styrene block copolymers.
  • the thermoplastic adhesives listed in paragraph [0027] of EP 1 475 424 A1 are used.
  • Other thermoplastic adhesives which are particularly suitable for special applications, such as the bonding of glass adhesion substrates, are described in EP 1 95 60 63 A2. Preference is given to using thermoplastic adhesives whose melt viscosity is increased by rheological additives, for example by addition of pyrogenic silicas, carbon black, carbon nanotubes and / or further polymers as blending components.
  • a reactive heat-activated adhesive composition advantageously comprises an elastomeric base polymer and a modification resin, wherein the modification resin comprises an adhesive resin and / or a reactive resin. Due to the use of an elastomeric base polymer, it is possible to obtain adhesive layers having excellent dimensional stability.
  • reactive heat-activated adhesive compositions can be used according to the respective specific applications, all known from the prior art heat-activated adhesive compositions bondable.
  • nitrile rubber gives the heat-activated bondable film due to its high flow viscosity a pronounced dimensional stability, which can be achieved after performing a crosslinking reaction high bond strengths on plastic surfaces.
  • the bondable polymer advantageously contains from 40 to 94% by weight of acrylic acid compounds and / or methacrylic acid compounds of the general formula CH 2 CC (R 1 ) (COOR 2 ) (R 1 represents a radical which is selected from the group comprising H and CH 3 , and R 2 represents a group selected from the group consisting of H and linear or branched alkyl chains having 1 to 30 carbon atoms), from 5 to 30% by weight of a first copolymerizable vinyl monomer having at least one acid group in particular a carboxylic acid group and / or sulfonic acid group and / or phosphonic acid group, from 1 to 10% by weight of a second copolymerizable vinyl monomer having at least one epoxy group or an acid anhydride function
  • Another useful reactive heat-activated adhesive composition which offers particular advantages comprises from 40 to 98% by weight of an acrylate-containing block copolymer, from 2 to 50% by weight of a resin component and from 0 to 10% by weight of a hardener component.
  • the resin component contains one or more resins selected from the group consisting of tackiness-enhancing (tackifying) epoxy resins, novolak resins, and phenolic resins.
  • the hardener component is used to crosslink the resins from the resin component. Due to the strong physical crosslinking within the polymer, such a formulation offers the particular advantage that adhesive layers having a greater overall thickness can be obtained without impairing the load-bearing capacity of the bond as a whole.
  • these adhesive layers are particularly suitable for compensating for unevenness in the substrate.
  • such an adhesive has a good resistance to aging and only low outgassing behavior, which is particularly desirable in many applications in the field of electronics.
  • Reactive pressure-sensitive adhesives in particular also those which are suitable for structural bonding, are also used to advantage.
  • Such adhesives disclose, for example, the publications DE 199 05 800 B4 and EP 0 881 271 B1, the relevant disclosure of which is intended to be included in the disclosure of this document.
  • both heat-activatable adhesives are selected such that after production of the bond by heating the heat-activatable bondable surface element by magnetic induction, the bond strength in the static shear test on polycarbonate is greater than 100 MPa, preferably between 100 and 300 MPa and quite more preferably greater than 400 MPa.
  • At least one of the two, but possibly also both, heat-activatable adhesives is only partially coated on the electrically conductive sheet, for example in the form of geometric surfaces (eg points, triangles, diamonds or hexagons) or linear patterns (eg webs, Lines, grids or waves). This allows a further differentiation of the separation force can be achieved on the two sides.
  • the heat-activatable adhesive layer layers are made differently thick. This has the advantage that differences in adhesive force of the various adhesives can be compensated by higher or lower layer thickness.
  • the at least one electrically conductive sheet can be of any suitable design, for example as a thin, full-surface-compact or perforated layer (for example as a grid).
  • the layer thickness of the electrically conductive layer is preferably less than 50 ⁇ m, in particular less than 20 ⁇ m or even less than 10 ⁇ m. The latter makes it possible to limit the heating speed upwards in a relatively simple manner.
  • each layer is considered to consist of at least one material which has a conductivity (electrons and / or holes) of at least 1 mS / m at a temperature of 23 ° C., so that an electrical current flow can occur therein.
  • a conductivity electrospray
  • these are in particular metals, semimetals and other metallic materials and optionally also semiconductors in which the electrical resistance is low.
  • the electrical resistance of the electrically conductive layer is high enough to allow the layer to flow when an electrical current flows in the layer, but on the other hand it is low enough to establish a current flow through the layer at all.
  • electrically conductive planar materials flat structures are preferably used, since they can be heated at low frequencies, which results in a higher penetration depth of the magnetic field and lower equipment costs.
  • these electrically conductive sheets have a thickness of less than 50 ⁇ m, in particular less than 20 ⁇ m, and in particular less than 10 ⁇ m, since the adhesive tapes become more flexible as the thickness of the electrically conductive sheet decreases.
  • very thin adhesive tapes can be made available;
  • the amount of remaining on the one joining part electrically conductive material can be reduced.
  • the electrically conductive layer of the heat-activated bondable surface element has a layer thickness of less than 20 ⁇ , in particular of less than ⁇ ⁇ ⁇ in order to limit its heating rate in a particularly simple manner.
  • the surface element can have a further heat-activated adhesive layer.
  • Such a surface element is as two-sided bondable surface element particularly suitable to connect two bonding substrates together.
  • the electrically conductive layer is preferably also magnetic, in particular ferromagnetic or paramagnetic. While it has been expected for such materials that in addition to induction of eddy currents, there will also be heating due to hysteresis losses and the overall heating rate will be greater, it has been observed that even magnetic materials such as nickel or magnetic steels conduct the electrical current well have consistently lower heating rates than materials that conduct the electrical current very well, but are not themselves magnetic, such as copper or aluminum. Therefore, by using magnetic materials that conduct electricity, it is easier to control heating and reduce the occurrence of heating effects away from the bondline.
  • the electrically conductive layer has an electrical conductivity of more than 20 MS / m (which can be achieved for example by using aluminum), in particular more than 40 MS / m (which, for example, by using copper or silver can be achieved), each determined for 300 K.
  • the required for the production of high strengths of the adhesive bond sufficiently high temperatures in the adhesive joint and a homogeneous heating can be realized even in very thin surface elements.
  • heating due to induced eddy currents increases with increasing conductivity and not, as expected, with increasing electrical resistance.
  • heat-activatable adhesive films based on different chemical bases have been used in undersized thicknesses (see table).
  • commercially available heat-activatable films tesa SE could be used in part.
  • bonding substrates for the adhesive tape 1 according to the invention 2 polycarbonate sheets 2 with a width of 20 mm, a length of 100 mm and a thickness of 3 mm were used, which overlapped in the glued joint 3 by 10 mm (see Fig. 1).
  • the bond area included here a rectangle of 10 x 20 mm edge length.
  • the joining partners were selected from the same material.
  • the lower punch element 4, the upper punch element 5 and the force F are also shown schematically.
  • the bonding process was carried out with the aid of a modified induction installation of type EW5F from IFF GmbH, Ismaning.
  • an induction field transformer which consists of only a water-cooled current-carrying conductor, which is used as a secondary coil circuit of a Transformatorfeldschreibtragers and in a coaxial transformer with the primary coil side generated transformer field interacts.
  • the induction field transformer was embedded in a matrix of polyetheretherketone (PEEK) and the arrangement thus obtained was used as the lower compression punch element 4 of a pressing device, which also has an upper punch element 5.
  • the pulse width indicates the percentage share of the pulse duration (pulse length) of the alternating magnetic field in the total period of time (the sum of the pulse duration and the duration of the pauses between two successive pulses) of the alternating magnetic field.
  • the bond strength in the dynamic tensile shear test was selected on the basis of DIN 53283 at 23 ° C. and a test speed of 1 mm / min. All experiments were repeated 10 times.
  • PA copolyamide

Abstract

The invention relates to a method for gluing together and detaching again two substrate surfaces, wherein a surface element that can be glued by heat activation is used for gluing. The surface element that can be glued by heat activation comprises at least one electrically conductive sheet material and at least two layers made of different heat-activatable adhesive compounds, wherein the first heat-activatable adhesive compound layer is substantially located on the one side of the electrically conductive sheet material and the second heat-activatable adhesive compound is substantially located on the other side of the electrically conductive sheet material. The method is characterized in that the gluing is effected by exposing the surface element that can be glued by heat activation to a temperature T1, at which a simultaneous heat activation of the two heat-activatable adhesive compounds takes place. The detachment is effected by exposing the gluing site to a temperature T2, at which under predetermined conditions only one of the heat-activatable layers of the surface element that can be glued by heat activation loses the adhesive effect thereof in the adhesive bond so much that the adhesive bond is separated.

Description

Induktiv erwärmbares Klebeband mit differentiellem Löseverhalten  Induction heatable adhesive tape with differential release behavior
Die Erfindung betrifft ein Verfahren zum Verkleben zweier Substrate, insbesondere zweier Kunststoffsubstrate, miteinander mittels hitzeaktivierberer Klebemassen, sowie weiterhin ein verfahren zum Wiederlösen des so entstandenen Verklebungsverbundes der Substarte miteinander. The invention relates to a method for bonding two substrates, in particular two plastic substrates, to each other by means of heat-activating adhesives, and furthermore to a method for re-dissolving the bonding composite of the substrate which has been produced in this way.
Hitzeaktiviert verklebbare Flächenelemente (hitzeaktivierbare Flächenelemente) werden eingesetzt, um hochfeste Verbindungen von Fügeteilen zu erhalten. Insbesondere eignen sich derartige Flächenelemente, um bei einer geringeren Dicke der Klebefuge vergleichbare oder höhere Festigkeiten zu erreichen als dies mit Flächenelementen möglich ist, die ausschließlich Haftklebemassensysteme enthalten. Derartige hochfeste Verklebungen sind insbesondere bei der voranschreitenden Miniaturisierung von elektronischen Geräten von Bedeutung, etwa im Bereich der Konsumgüterelektronik, der Unterhaltungselektronik oder der Kommunikationselektronik, zum Beispiel für Mobiltelefone, PDAs, Laptops und andere Rechner, Digitalkameras und Anzeigegeräte wie etwa Displays und Digitalreader. Heat-activated, bondable surface elements (heat-activated surface elements) are used to obtain high-strength joints of parts to be joined. In particular, such surface elements are suitable to achieve comparable or higher strengths at a smaller thickness of the adhesive joint than is possible with surface elements which contain exclusively PSA systems. Such high strength bonds are particularly important in the advancing miniaturization of electronic devices, such as consumer electronics, consumer electronics, or communications electronics, for example, cell phones, PDAs, laptops and other computers, digital cameras, and display devices such as displays and digital readers.
In besonderem Maße steigen die Anforderungen an die Verarbeitbarkeit und Stabilität von Klebeverbindungen bei tragbaren Konsumgüterelektronikartikeln. Dies liegt zum einen daran, dass die Abmessungen solcher Artikel immer geringer werden, so dass sich auch die für eine Klebeverbindung nutzbare Fläche verringert. Zum anderen muss eine Klebeverbindung in derartigen Geräten besonders stabil sein, da tragbare Artikel starken mechanischen Belastungen wie etwa Stößen oder Stürzen standhalten müssen und zudem in einem breiten Temperaturbereich eingesetzt werden sollen. In particular, the demands on the processability and stability of adhesive bonds in consumer electronic consumer goods are increasing. This is due, on the one hand, to the fact that the dimensions of such articles are becoming ever smaller, so that the usable area for an adhesive bond is also reduced. On the other hand, an adhesive bond in such devices must be particularly stable because portable articles must withstand strong mechanical stresses such as impacts or falls and also be used in a wide temperature range.
Daher werden in derartigen Produkten bevorzugt hitzeaktiviert verklebbare Flächenelemente eingesetzt, die hitzeaktiviert verklebende Klebemassen aufweisen, also Klebemassen, die bei Raumtemperatur keine oder eine allenfalls geringe Eigenklebrigkeit aufweisen, unter Einwirkung von Hitze aber die für eine Verklebung erforderliche Klebkraft zu den jeweiligen Verklebungssubstraten (Fügepartnern, Haftgrund) aufbauen. Solche hitzeaktiviert verklebenden Klebemassen liegen bei Raumtemperatur häufig in fester Form vor, werden während des Verklebens aber durch Temperatureinwirkung entweder reversibel oder irreversibel in einen Zustand hoher Klebkraft überführt. Reversibel hitzeaktiviert verklebende Klebemassen sind zum Beispiel Klebemassen auf der Basis thermoplastischer Polymere, wohingegen irreversibel hitzeaktiviert verklebende Klebemassen etwa Reaktivklebemassen sind, in denen infolge einer thermischen Aktivierung chemische Reaktionen wie beispielsweise Vernetzungsreaktionen ablaufen, wodurch diese Klebemassen besonders für permanente hochfeste Verklebungen geeignet sind. Therefore, in such products preferably heat-activated adhesive surface elements are used which have heat-activated adhesive adhesives, ie adhesives which have no or at most low Eigenklebrigkeit at room temperature, under the action of heat but the adhesive force required for bonding to the respective Build bonding substrates (joining partners, primer). Such heat-activated adhesive adhesives are often present in solid form at room temperature, but are transferred to a state of high bond strength either reversibly or irreversibly during bonding by the action of temperature. Reversibly heat-activated adhesive adhesives are, for example, adhesives based on thermoplastic polymers, whereas adhesives that are irreversibly heat-activated are reactive adhesives in which, as a result of thermal activation, chemical reactions such as crosslinking occur, whereby these adhesives are particularly suitable for permanent high-strength adhesions.
Um hitzeaktivierbare Klebebänder an zwei Fügepartner aus unterschiedlichen Materialien anzupassen, beispielsweise aus Metall und Kunststoff, ist es im Stand der Technik bekannt, ein mehrschichtiges, auf jeder Seite jeweils unterschiedliche hitzeaktivierbare Klebmassen enthaltendes Klebeband zu verwenden (siehe z.B. die Schrift DE 10 2006 055 093 A1 ). Solcherart mehrschichtige hitzeaktivierbare Klebebänder werden auch in Bereichen eingesetzt, in denen haftklebrige Eigenschaften in hitzeaktivierbare Klebebänder eingebracht werden sollen, etwa um die Fügeteile in Position zu halten. Hier ist zumindest eine Schicht zumindest partiell als Haftkleber ausgeführt, der in speziellen Fällen auch durch eine chemische Reaktion - die in der Regel hitzeaktiviert wird - in einen nicht haftklebrigen Zustand überführt werden kann (vgl. z.B. die EP 1 078 965 A2 und die US 4,120,712 A) In order to adapt heat-activatable adhesive tapes to two joining partners made of different materials, for example of metal and plastic, it is known in the prior art to use a multi-layered adhesive tape containing different heat-activatable adhesives on each side (see, for example, DE 10 2006 055 093 A1 ). Such multilayer heat-activatable adhesive tapes are also used in areas in which pressure-sensitive adhesive properties are to be introduced into heat-activatable adhesive tapes, for example in order to hold the joining parts in position. Here, at least one layer is at least partially designed as a pressure-sensitive adhesive, which in special cases can also be converted into a non-tacky state by a chemical reaction-which as a rule is heat-activated (cf., for example, EP 1 078 965 A2 and US Pat. No. 4,120,712) A)
Bekannt ist auch, aus Klebebändern der Geometrie der Klebefuge angepasste Stanzlinge herzustellen. Zur Verbesserung der Stanzbarkeit von hitzeaktivierbaren Folien werden innenliegende Kunststofffolien vorgeschlagen, welche auf jeder Seite mit jeweils einer hitzeaktivierbaren Klebmasse versehen sind, die auch verschieden sein können. It is also known to produce stampings adapted from adhesive tapes to the geometry of the glue joint. To improve the stampability of heat-activatable films internal plastic films are proposed, which are each provided with a heat-activatable adhesive on each side, which may also be different.
Allen hitzeaktiviert verklebenden Klebemassensystemen ist gemeinsam, dass diese beim Verkleben erhitzt werden müssen. Insbesondere bei Verklebungen, bei denen die Klebemassensysteme nach außen hin von den Verklebungssubstraten vollflächig abgedeckt sind, ist es besonders wichtig, die zum Aufschmelzen oder zur Aktivierung der Klebemasse erforderliche Wärme schnell zu der Verklebungsfläche hin zu transportieren. Ist dabei eines der Verklebungssubstrate ein guter Wärmeleiter, so ist es möglich, dieses Verklebungssubstrat durch eine externe Wärmequelle zu erwärmen, beispielsweise durch einen direkten Wärmeübertrager, eine Infrarotheizung oder dergleichen. Die für eine schnelle homogene Erwärmung der bekannten Klebemasse erforderliche kurze Aufheizzeit lässt sich im Falle eines solchen direkten Erhitzens oder Kontakterhitzens allerdings nur für einen großen Temperaturgradienten zwischen der Wärmequelle und dem Verklebungssubstrat realisieren. Daher sollte das zu erwärmende Verklebungssubstrat selber gegenüber Temperaturen unempfindlich sein, die zum Teil sogar erheblich höher ausfallen können als es das Aufschmelzen oder Aktivieren der Klebemasse eigentlich erfordern würde. Problematisch ist also der Einsatz hitzeaktivierbarer Klebefolien für Kunststoff-Kunststoff-Verklebungen. Als Kunststoffe werden insbesondere in der Konsumgüterelektronik beispielsweise Polyvinylchlorid (PVC), Acrylnitril-Butadien-Styrol- Copolymere (ABS), Polycarbonate (PC), Polypropylen (PP) oder Blends basierend auf diesen Kunststoffen eingesetzt. All heat-activated bonding adhesive systems have in common that they must be heated during bonding. Particularly in the case of adhesions in which the adhesive composition systems are covered over the entire surface of the bonding substrates to the outside, it is particularly important to quickly transport the heat required for melting or activation of the adhesive to the bonding surface. If one of the bonding substrates is a good heat conductor, it is possible to heat this bonding substrate by an external heat source, for example by a direct heat exchanger, an infrared heater or the like. However, in the case of such direct heating or contact heating, the short heating time required for rapid, homogeneous heating of the known adhesive can only be realized for a large temperature gradient between the heat source and the bonding substrate. Therefore, the bonding substrate to be heated itself should be insensitive to temperatures which may in some cases even be significantly higher than would actually require the melting or activation of the adhesive. The problem is therefore the use of heat-activated adhesive films for plastic-plastic bonds. As plastics, for example, in the consumer goods electronics, for example, polyvinyl chloride (PVC), acrylonitrile-butadiene-styrene copolymers (ABS), polycarbonates (PC), polypropylene (PP) or blends based on these plastics are used.
Anders ist die Situation also, wenn keines der Verklebungssubstrate die Wärme hinreichend gut leitet oder wenn die Verklebungssubstrate gegenüber höheren Temperaturen empfindlich sind, wie dies zum Beispiel bei vielen Kunststoffen der Fall ist, aber auch bei elektronischen Bauteilen wie etwa Halbleiterbauteilen oder Flüssigkristallmodulen. Zur Verklebung von Verklebungssubstraten aus wenig thermisch leitfähigen oder wärmeempfindlichen Materialien bietet es sich daher an, das hitzeaktiviert verklebbare Flächenelement selbst mit einem intrinsischen Mechanismus zum Heizen auszurüsten, so dass die zum Verkleben erforderliche Wärme nicht von außen eingebracht werden muss, sondern direkt im Innern des Flächenelements selber erzeugt wird. Aus dem Stand der Technik sind unterschiedliche Mechanismen bekannt, mittels derer sich ein derartiges internes Erwärmen realisieren lässt, etwa als Erwärmen mittels einer elektrischen Widerstandsheizung, durch magnetische Induktion oder infolge einer Wechselwirkung mit Mikrowellenstrahlung.  Thus, the situation is different if none of the bonding substrates conducts the heat sufficiently well or if the bonding substrates are sensitive to higher temperatures, as is the case for many plastics, but also electronic components such as semiconductor devices or liquid crystal modules. For bonding bonding substrates of less thermally conductive or heat-sensitive materials, it is therefore appropriate to equip the heat-activated glued surface element itself with an intrinsic mechanism for heating, so that the heat required for bonding need not be introduced from the outside, but directly inside the surface element itself is generated. Various mechanisms are known from the prior art, by means of which such an internal heating can be realized, such as heating by means of an electrical resistance heating, by magnetic induction or as a result of an interaction with microwave radiation.
Die Erwärmung im magnetischen Wechselfeld wird zum Einen durch induzierte Wirbelströme in elektrisch leitfähigen Rezeptoren, zum Anderen - modellhaft erklärt - durch Hystereseverluste der umklappenden Elementarmagnete im Wechselfeld erreicht. Für das Ausbilden von Wirbelströmen ist allerdings eine Mindestgröße der leitfähigen Domänen erforderlich. Diese Mindestgröße steigt, je geringer die Frequenz des Wechselfeldes ist. Je nach Rezeptormaterial treten beide Effekte gemeinsam (z.B. magnetische Metalle) oder jeweils nur ein Effekt (z.B. Aluminium: nur Wirbelströme; Eisenoxidpartikel: nur Hyterese) auf. The heating in the alternating magnetic field is on the one hand by induced eddy currents in electrically conductive receptors, on the other - model - explained - achieved by hysteresis losses of the umklappenden elementary magnets in the alternating field. For the formation of eddy currents, however, a minimum size of the conductive domains is required. This minimum size increases the lower the frequency of the alternating field. Depending on the receptor material, both effects occur together (e.g., magnetic metals) or only one effect at a time (e.g., aluminum: eddy only, iron oxide particles: hyteresis only).
Grundsätzlich sind verschiedene Erhitzungsvorrichtungen für eine induktive Erwärmung bekannt; diese lassen sich unter anderem nach den Frequenzen unterscheiden, die das mit der jeweiligen Erhitzungsvorrichtung erzeugte Magnet-Wechselfeld besitzt. So kann eine Induktionserwärmung unter Verwendung eines Magnetfeldes erfolgen, dessen Frequenz im Frequenzbereich von etwa 100 Hz bis etwa 200 kHz liegt (den so genannten Mittelfrequenzen; MF) oder auch im Frequenzbereich von etwa 300 kHz bis etwa 100 MHz liegt (den so genannten Hochfrequenzen; HF). Darüber hinaus sind als Sonderfall auch Erhitzungsvorrichtungen bekannt, deren Magnetfeld eine Frequenz aus dem Bereich der Mikrowellen besitzt, beispielsweise die Mikrowellen-Standardfrequenz von 2,45 GHz. In principle, various heating devices for inductive heating are known; These can be distinguished among other things according to the frequencies that has the magnetic alternating field generated by the respective heating device. Thus, an induction heating can be done using a magnetic field whose frequency in the Frequency range from about 100 Hz to about 200 kHz (the so-called center frequencies, MF) or in the frequency range from about 300 kHz to about 100 MHz (the so-called high frequencies, HF). In addition, as a special case, heating devices are known whose magnetic field has a frequency from the range of microwaves, for example, the microwave standard frequency of 2.45 GHz.
Mit der Frequenz des eingesetzten Wechselfeldes steigt der technische Aufwand, der betrieben werden muss, um das Wechselfeld zu erzeugen, und damit die Kosten für die Erhitzungsvorrichtung. Während Mittelfrequenzanlagen derzeit bereits zu einem Marktpreis von etwa 5.000 Euro erhältlich sind, sind für Hochfrequenzanlagen mindestens 25.000 Euro zu berücksichtigen. Darüber hinaus steigen auch die Sicherheitsanforderungen an die Erwärmungsanlage mit der Frequenz, so dass bei Hochfrequenzanlagen zusätzlich zu den höheren Anschaffungskosten regelmäßig auch höhere Kosten für die Installation einer solchen Anlagentechnik anfallen. With the frequency of the alternating field used increases the technical effort that must be operated to generate the alternating field, and thus the cost of the heating device. While medium-frequency systems are currently available at a market price of around 5,000 euros, at least 25,000 euros have to be considered for high-frequency systems. In addition, the safety requirements for the heating system with the frequency rise, so that in high-frequency systems in addition to the higher initial costs regularly incurred higher costs for the installation of such equipment.
Bei der Verwendung von hohen Frequenzen zur Verklebung von Bauteilen in elektronischen Geräten können zudem unerwünschte Schädigungen elektronischer Bauteile in diesen Geräten während der Beaufschlagung mit dem elektromagnetischen Wechselfeld auftreten. When using high frequencies for bonding components in electronic devices, undesired damage to electronic components in these devices during exposure to the alternating electromagnetic field can also occur.
Als Anwendungsbeispiele für die Induktionserwärmung können Fertigungsprozesse aus den Bereichen Kleben, Nahtabdichten, Härten, Anlassen und Ähnlichem dienen. Die gängige Technik dabei ist, solche Verfahren anzuwenden, bei denen die Induktoren Bauteile komplett oder teilweise umfassen und über den ganzen Umfang gleichmäßig oder beim Bedarf absichtlich ungleichmäßig erwärmen, z. B. nach der EP 1 056 312 A2 oder der DE 20 2007 003 450 U1. As application examples for induction heating, manufacturing processes from the fields of gluing, seam sealing, hardening, tempering and the like can serve. The common technique is to use such methods in which the inductors comprise components completely or partially and uniformly over the entire circumference or intentionally unevenly heat when needed, eg. Example, according to EP 1 056 312 A2 or DE 20 2007 003 450 U1.
In der DE 20 2007 003 450 U1 wird beispielsweise auch ein Verfahren zum Verschmelzen einer Behälteröffnung mit einer Siegelfolie dargestellt, bei dem die metallische Einlage einer Siegelfolie mittels Induktion erwärmt wird und durch Wärmeleitung ein Siegelkleber aufgeschmolzen wird. Die Behälter sind durch einen aufschraubbaren oder einrastbaren Deckel verschlossen, der eine Metallfolie und eine benachbart angeordnete Kunststoff- Siegelfolie enthält. Mit Hilfe der Induktionsspule werden in der Metallfolie Wirbelströme erzeugt, welche die Metallfolie erwärmen. Durch den Kontakt zwischen Metall- und Siegelfolie wird auch die Siegelfolie erwärmt und dadurch mit der Behälteröffnung verschmolzen. Tunnelförmige Induktionsspulen weisen gegenüber flachen Spulen den Vorteil auf, dass auch Behälter mit einem großen Abstand zwischen der Metallfolie und der Deckeloberkante versiegelt werden können, da die Spule von der Seite auf die Metallfolie einwirkt. In DE 20 2007 003 450 U1, for example, a method for fusing a container opening with a sealing film is shown, in which the metallic insert of a sealing film is heated by induction and by heat conduction a sealant is melted. The containers are closed by a screw-on or latchable lid, which contains a metal foil and a plastic sealing film arranged adjacently. With the help of the induction coil eddy currents are generated in the metal foil, which heat the metal foil. Due to the contact between the metal foil and the sealing foil, the sealing foil is also heated and thereby fused with the container opening. Tunnel-shaped induction coils have the advantage over flat coils that also containers with a large distance between the metal foil and the Cover upper edge can be sealed because the coil acts from the side of the metal foil.
Nachteilig an diesem Verfahren ist, dass ein wesentlich größerer Teil des Bauteilvolumens als das reine Klebervolumen und die Metallfolie durch das elektromagnetische Feld geführt wird und somit im Falle eines elektronischen Bauteils Schädigungen nicht ausgeschlossen sind, da an unerwünschten Stellen Erwärmungen auftreten können. Weiterhin nachteilig ist, dass die gesamte Deckefolie aufgeheizt wird, wobei für die Verklebung nur der im Kontakt mit dem Behälter stehende Randbereich ausreichend wäre. Somit ergibt sich ein großes Verhältnis von aufgeheizter Fläche zu Verklebungsfläche, welches für typische Getränkeflaschen mit einem Öffnungsdurchmesser von 25 mm und einer Verklebungsbreite von 2 mm etwa bei 6,5 liegt. Für größere Behälterdurchmesser bei in der Regel gleichbleibender Verklebungsbreite erhöht sich das Verhältnis.  A disadvantage of this method is that a much larger part of the component volume than the pure adhesive volume and the metal foil is guided by the electromagnetic field and thus damages are not excluded in the case of an electronic component, since heating can occur at undesirable points. A further disadvantage is that the entire cover sheet is heated, with only the edge area in contact with the container being sufficient for the bonding. This results in a large ratio of heated area to bonding area, which is about 6.5 for typical beverage bottles with an opening diameter of 25 mm and a bond width of 2 mm. For larger container diameter with usually constant bond width increases the ratio.
In den letzten Jahren sind für das induktive Erwärmen insbesondere beim Verkleben von Kunststoff auf Kunststoff induktiv erwärmbare hitzeaktivierbare Klebefolien (HAFs) erneut in das Zentrum der Aufmerksamkeit gerückt. Der Grund hierfür ist den nunmehr verfügbaren nanopartikulären Systemen wie zum Beispiel MagSilica™ (Evonik AG) zu suchen, die in das Material des zu erwärmenden Körper eingearbeitet werden können und so ein Erwärmen des Körpers über sein gesamtes Volumen ermöglichen, ohne dass dessen mechanische Stabilität dadurch in nennenswerter Weise beeinträchtigt wird. In recent years, inductively heatable heat-activatable adhesive films (HAFs), which can be inductively heat-activated adhesive foils (HAFs), have again become the focus of attention for inductive heating, especially when bonding plastic to plastic. The reason for this is to look for the now available nanoparticulate systems, such as MagSilica ™ (Evonik AG), which can be incorporated into the material of the body to be heated and thus allow the body to heat up over its entire volume, without its mechanical stability thereby is appreciably affected.
Aufgrund der geringen Größe dieser nanoskopischen Systeme ist es jedoch nicht möglich, derartige Produkte in Magnet-Wechselfeldern mit Frequenzen aus dem Mittelfrequenzbereich effizient zu erwärmen. Vielmehr sind für die neuartigen Systeme Frequenzen aus dem Hochfrequenzbereich erforderlich. Grade bei diesen Frequenzen tritt jedoch das Problem einer Beschädigung von elektronischen Bauteilen im Magnet- Wechselfeld besonders stark zutage. Die Erzeugung von Magnet-Wechselfeldern mit Frequenzen im Hochfrequenzbereich erfordert überdies einen erhöhten apparativen Aufwand und ist somit ökonomisch ungünstig. Zudem ist die Verwendung von nanopartikulären Füllstoffen auch in ökologischer Hinsicht problematisch, da sich diese bei einem späteren Recycling kaum von den umgebenden Materialien abtrennen lassen. Darüber hinaus ist es nur schwer möglich, diese Partikel in sehr dünnen Filmen einzusetzen, da infolge der starken Neigung nanopartikulärer Systeme zur Agglomeratbildung die hiermit erzeugten Filme zumeist stark inhomogen sind. Weiterhin und zur Vermeidung der vorstehenden Problematik können hitzeaktivierbare Folien (HAFs), die induktiv erwärmbar sein sollen, mit metallischen oder metallisierten Flächengebilden gefüllt sein. Dies ist bei der Verwendung von vollflächigen Metallfolien auch im Mittelfrequenzbereich sehr effizient, hohe Erwärmungsraten können erreicht werden, so dass Induktionszeiten zwischen 0,05 und 10 s realisiert werden können. Dabei ist auch die Verwendung von sehr dünnen leitfähigen Folien zwischen 0,25 μηι und 75 μηι möglich. However, due to the small size of these nanoscopic systems, it is not possible to efficiently heat such products in magnetic alternating fields with frequencies from the mid-frequency range. Instead, frequencies from the high-frequency range are required for the novel systems. However, it is at these frequencies that the problem of damage to electronic components in the alternating magnetic field is particularly evident. The generation of alternating magnetic fields with frequencies in the high-frequency range also requires an increased expenditure on equipment and is thus economically unfavorable. In addition, the use of nanoparticulate fillers is also environmentally problematic because they can hardly be separated from the surrounding materials in a later recycling. In addition, it is difficult to use these particles in very thin films, since due to the strong tendency of nanoparticulate systems for agglomeration, the films produced here are mostly highly inhomogeneous. Furthermore, and to avoid the above problem, heat-activatable films (HAFs), which are to be heated inductively, may be filled with metallic or metallized sheets. This is also very efficient in the middle frequency range when using full-surface metal foils, high heating rates can be achieved, so that induction times between 0.05 and 10 s can be realized. It is also the use of very thin conductive films between 0.25 μηι and 75 μηι possible.
Bekannt ist auch der Einsatz von durchbrochenen Metallfolien, Drahtnetzen, Streckmetall, Metallvliesen oder Fasern, durch die das Matrixmaterial der HAF hindurchdringen kann, so dass die Kohäsion des Verbunds verbessert wird. Die Effizienz der Erwärmung nimmt dadurch allerdings ab. Also known is the use of apertured metal foils, wire nets, expanded metal, metal nonwovens or fibers through which the matrix material of the HAF can penetrate, thus improving the cohesiveness of the composite. However, the efficiency of heating decreases.
Für Verklebungen innerhalb mobiler elektronischer Geräte ist das mit induktiv erwärmbaren Nanopartikeln ausgestattete Produkt Duolplocoll RCD der Firma Lohmann bekannt. Dieses ist ausschließlich im Hochfrequenzbereich technisch nutzbar zu erwärmen. Die oben beschriebenen Nachteile der Verwendung von Partikeln und hochfrequenten Wechselfeldern treffen auch auf dieses Produkt zu. Für dieses Produkt wird auch die Möglichkeit der Lösung von damit hergestellten Klebverbindungen mittels erneuter induktiver Erwärmung dargestellt. Nachteilig an solcherart partikelgefüllten Klebebändern ist, dass bei hoher Erwärmung die Kohäsion nachlässt und sich somit nach der Trennung der Bauteile Klebebandreste auf beiden Fügepartnern befinden, welche jeweils mit Partikeln kontaminiert sind. Dies ist für ein stoffliches Recycling ungünstig. For bonding within mobile electronic devices, the product Duolplocoll RCD from Lohmann equipped with inductively heatable nanoparticles is known. This can only be used technically in the high-frequency range to heat. The above-described disadvantages of the use of particles and high-frequency alternating fields also apply to this product. For this product, the possibility of solving adhesive bonds produced by means of re-inductive heating is also presented. A disadvantage of such particle-filled adhesive tapes is that at high heating, the cohesion subsides and thus after separation of the components are adhesive tape residues on both joining partners, which are each contaminated with particles. This is unfavorable for material recycling.
Die Trennung zusammengeklebter Bauteile mittels Induktionserwärmung ist im Stand der Technik bekannt. Vielfach werden dabei ebenfalls partikelbasierte Klebersysteme mit den oben beschriebenen Nachteilen verwendet. Für flächige Suszeptormaterialien wird dies in EP 1 453 360 A2 beschrieben. The separation of glued together components by means of induction heating is known in the art. In many cases, particle-based adhesive systems with the disadvantages described above are also used. For areal susceptor materials, this is described in EP 1 453 360 A2.
Bei der Verwendung von flächigen Gebilden zur Erzeugung der Wärme im magnetischen Wechselfeld ergibt sich das Problem, dass bei einer Lösung der Verbindung durch thermische Effekte (z.B. Aufschmelzen oder chemische Dekomposition) nicht sicher vorausgesagt werden kann, auf welchem der Fügepartner das innenliegende wärmeerzeugende Flächengebilde haften bleiben wird. Daher ergeben sich auch hier Schwierigkeiten durch Kontamination beim stofflichen Recycling. When using sheet-like structures for generating the heat in the alternating magnetic field there is the problem that in a solution of the compound by thermal effects (eg melting or chemical decomposition) can not be predicted with certainty on which of the joining partners adhere to the internal heat-generating sheet becomes. Therefore, difficulties arise here due to contamination during recycling.
Aufgabe der vorliegenden Erfindung war es, ein Material und Verfahren zur Verfügung zu stellen, mit dem Verklebungen, insbesondere Kunststoff-Kunststoff-Verklebungen unter Vermeidung der Nachteile des Stands der Technik hergestellt und kontrolliert wieder getrennt werden können. Object of the present invention was to provide a material and methods available, with the bonding, in particular plastic-plastic bonds under Avoiding the disadvantages of the prior art produced and controlled again can be separated.
Gelöst wird die Aufgabe durch ein Verfahren zum Verkleben (so dass ein Klebeverbund entsteht) und Wiederlösen (so dass der Klebeverbund wieder getrennt wird) zweier Substratoberflächen, wobei für die Verklebung ein hitzeaktiviert verklebbares Flächenelement eingesetzt wird, das hitzeaktiviert verklebbare Flächenelement zumindest ein elektrisch leitfähiges Flächengebilde sowie zumindest zwei Schichten unterschiedlicher hitzeaktivierbarer Klebmassen umfasst, wobei sich die erste hitzeaktivierbare Klebmassenschicht im Wesentlichen auf der einen Seite des elektrisch leitfähigen Flächengebildes und die zweite hitzeaktivierbare Klebmasse im Wesentlichen auf der anderen Seite des elektrisch leitfähigen Flächengebildes befindet, dadurch gekennzeichnet, dass The object is achieved by a method for bonding (so that an adhesive bond is formed) and redissolving (so that the adhesive bond is separated again) of two substrate surfaces, wherein for bonding a heat-activated glued surface element is used, the heat-activated glued surface element at least one electrically conductive sheet and at least two layers of different heat-activatable adhesives, wherein the first heat-activatable adhesive layer is substantially on one side of the electrically conductive sheet and the second heat-activatable adhesive is substantially on the other side of the electrically conductive sheet, characterized in that
die Verklebung dadurch bewirkt wird, dass das hitzeaktiviert verklebbare Flächenelement einer ersten Temperatur (T-i) ausgesetzt wird, bei der eine gleichzeitige Hitzeaktivierung der beiden hitzeaktivierbaren Klebmassen erfolgt,  the bonding is effected by subjecting the heat-activated, bondable surface element to a first temperature (T-i) at which a simultaneous heat activation of the two heat-activatable adhesives takes place,
das Wiederlösen dadurch bewirkt wird, das die Verklebungsstelle (also insbesondere das hitzeaktiviert verklebte Flächenelement) einer zweiten Temperatur (T2) ausgesetzt wird, bei der unter vorgegebenen Bedingungen lediglich eine der hitzeaktivierbaren Schichten (im weiteren - lediglich zur sprachlichen Unterscheidung - als„erste hitzeaktivierbare Klebmasse" bezeichnet) des hitzeaktivierbaren Flächenelementes ihre Klebewirkung im Klebeverbund soweit verliert, das der Klebeverbund getrennt wird. the redissolution is effected by the bonding point (ie in particular the heat-activated bonded surface element) being exposed to a second temperature (T 2 ) under which only one of the heat-activatable layers (hereinafter - merely for language distinction) is designated as the first heat-activatable layer Adhesive "referred to) of the heat-activated surface element loses its adhesive effect in the adhesive bond as far as the adhesive bond is separated.
Im Sinne dieser Anmeldung wird einheitlich von hitzeaktivierbaren Klebmassen und von einem hitzeaktiviert verklebbaren Flächenelement auch dann gesprochen, wenn diese Bausteine sich im verklebten Zustand befinden bzw. nach der Wiederlösung des Klebeverbundes, unabhängig davon, ob die Eignung zu hitzeaktivierbaren Verklebung zu diesem Zeitpunkt noch besteht oder nicht. Damit wird der Tatsache Rechnung getragen, dass die Eignung zur hitzeaktivierbaren Verklebung vor der Verklebung bestand, und dass der jeweilige Gegenstand (ggf. in modifizierter, insbesondere verklebter) Form an sich weiter besteht, solange dieser Ausdruck verwendet wird. For the purposes of this application is uniformly spoken of heat-activatable adhesives and a heat-activated glued surface element even if these blocks are in the bonded state or after the re-solution of the adhesive bond, regardless of whether the suitability for heat-activable bonding at this time still exists or Not. This takes into account the fact that the suitability for heat-activatable bonding existed before the bonding, and that the respective article (if necessary in a modified, in particular bonded) form persists per se, as long as this term is used.
Sofern es relevant ist, in wieweit die Eignung im konkreten Zustand vorliegt oder nicht, wird dieses an den entsprechenden Textstellen deutlich gemacht.  If it is relevant to what extent the suitability is in the concrete state or not, this is made clear in the corresponding passages.
In sofern umfasst beispielsweise die Bezeichnung „hitzeaktiviert verklebbares Flächenelement" in den entsprechenden Fällen auch „hitzeaktiviert verklebte Flächenelemente", sofern nichts anderen beschrieben ist. Vor dem Einsatz des Flächenelementes handelt es sich jedenfalls um ein „hitzeaktiviert verklebbares Flächenelement" sowie bei den hitzeaktivierbaren Klebmassen um solche Klebmassen, die durch Erreichen einer Aktivierungstemperatur oberhalb der Raumtemperatur die Eignung zur Verklebung im Sinne der Anwendung ausbilden können. In this case, for example, the term "heat-activated adhesive surface element" in the corresponding cases also includes "heat-activated bonded surface elements", unless otherwise described. Before the use of the surface element is in any case a "heat-activated adhesive surface element" and the heat-activatable adhesives to such adhesives that can form the suitability for bonding in the sense of application by reaching an activation temperature above room temperature.
Die Bezeichnung „die hitzeaktivierbare Klebmasse befindet sich im Wesentlichen auf einer Seite des Flächengebildes" bedeutet, dass die Klebmasse auf der jeweiligen Flächenelement-Seite die Verklebung vollständig oder zum Größten teil bewirkt, sich aber im konkreten Klebebandaufbau durchaus auch auf die andere Seite des elektrisch leitfähigen Flächengebildes erstrecken kann, zum Beispiel durch Überlappung an den Flächengebilde- Kanten, durch Ineinanderfließen mit der gegenüberliegenden hitzeaktivierbaren Klebmasse, zum Beispiel bei unterbrochenen elektrisch leitfähigen Flächengebilden, wie Gittern, Lochplatten und dergleichen, oder auf andere Weise, jedenfalls in soweit, als das die Verwirklichung der erfinderischen Idee hierdurch nicht beeinflusst wird. „Im Wesentlichen" berücksichtigt also den Sachverhalt, dass sich die jeweilige hitzeaktivierbare Klebmasse vollständig auf der jeweiligen Seite des elektrisch leitfähigen Flächengebildes befinden kann, aber nicht muss, soweit gewährleistet bleibt, dass die Verklebung des hitzeaktiviert verklebbaren Flächenelementes auf dem jeweiligen Substrat maßgeblich durch die jeweilige hitzeaktivierbare Klebmasse maßgeblich gewährleistet bleibt. The term "the heat-activatable adhesive is essentially located on one side of the sheet" means that the adhesive on the respective surface element side causes the bonding completely or for the most part, but in concrete tape construction on the other side of the electrically conductive Sheet may extend, for example, by overlapping the sheet edges, by flowing into each other with the opposite heat-activatable adhesive, for example, in interrupted electrically conductive sheets, such as gratings, perforated plates and the like, or otherwise, at least insofar as that the realization The inventive concept is therefore not influenced by this "essentially" takes into account the fact that the respective heat-activatable adhesive can be completely on the respective side of the electrically conductive fabric, but not mu ss, as far as it is ensured that the bonding of the heat-activated bondable surface element on the respective substrate is significantly ensured by the respective heat-activatable adhesive significantly.
Als Flächenelement im Sinne dieser Anmeldung gelten insbesondere alle üblichen und geeigneten Gebilde mit im Wesentlichen flächenförmiger Ausdehnung. Diese ermöglichen eine flächige Verklebung und können verschieden ausgestaltet sein, insbesondere flexibel, als Klebefolie, Klebeband, Klebeetikett oder als Formstanzling. Das Flächenelement kann als zugeschnittenes Flächenelement ausgebildet sein, dessen Form an die Form der Verklebungsfläche angepasst ist, um die Gefahr zu verringern, dass das Verklebungssubstrat im Verlauf der induktiven Erwärmung thermisch beschädigt wird. As a surface element in the context of this application, in particular all conventional and suitable structures apply with substantially sheet-like extent. These allow a surface bonding and can be configured differently, in particular flexible, as an adhesive film, adhesive tape, adhesive label or as Formstanzling. The surface element may be formed as a cut surface element whose shape is adapted to the shape of the bonding surface in order to reduce the risk that the bonding substrate is thermally damaged in the course of inductive heating.
Flächenelemente im Sinne dieser Anmeldung weisen jeweils zwei Seitenflächen auf, eine Vorderseite und eine Rückseite. Die Begriffe Vorderseite und Rückseite beziehen sich dabei auf die beiden Oberflächen des Flächenelements parallel zu seiner Hauptausdehnung (Flächenausdehnung, Hauptausdehnungsebene) und dienen lediglich der Unterscheidung dieser beiden auf gegenüberliegenden Seiten des Flächenelements angeordneten Flächen, ohne dass durch die Wahl der Begriffe die absolute räumliche Anordnung der beiden Flächen festgelegt ist; demzufolge kann die Vorderseite auch die räumlich hinten gelegene Seitenfläche des Flächenelements darstellen, nämlich wenn dementsprechend die Rückseite dessen räumlich vorne gelegene Seitenfläche bildet. Dieses hitzeaktiviert verklebbare Flächenelement soll zwei Verklebungssubstrate miteinander verkleben. Dafür weist das Flächenelement an beiden Seitenflächen eine hitzeaktiviert verklebbare Klebmasse auf. Hitzeaktiviert verklebbare Klebmassen sind alle Klebmassen, die bei erhöhten Temperaturen heiß verklebt werden und nach dem Erkalten eine mechanisch belastbare Verbindung bieten. Üblicherweise liegt die Klebmasse in Form einer Klebmassenschicht vor. Surface elements in the sense of this application each have two side surfaces, a front and a back. The terms front and back refer to the two surfaces of the surface element parallel to its main extent (surface extent, main extension plane) and serve only to distinguish these two arranged on opposite sides of the surface element surfaces, without that by the choice of terms, the absolute spatial arrangement of both surfaces is set; Consequently, the front side can also represent the spatially rearward side surface of the surface element, namely, accordingly, when the back side forms its spatially front side surface. This heat-activated adhesive surface element is intended to glue two bonding substrates together. For this purpose, the surface element on both side surfaces on a heat-activated glued adhesive. Heat-activated adhesives that can be bonded are all adhesives which are hot-bonded at elevated temperatures and, after cooling, provide a mechanically strong bond. Usually, the adhesive is in the form of an adhesive layer.
Als Schicht wird insbesondere eine flächenförmige Anordnung eines Systems einheitlicher Funktionalität bezeichnet, deren Abmessungen in einer Raumrichtung (Dicke oder Höhe) signifikant kleiner sind als in den beiden anderen Raumrichtungen, die die Hauptausdehnung definieren (Länge und Breite). Eine derartige Schicht kann kompakt oder auch durchbrochen ausgebildet sein und aus einem einzigen Material oder aus unterschiedlichen Materialien bestehen, insbesondere, wenn diese zur einheitlichen Funktionalität dieser Schicht beitragen. Eine Schicht kann eine über ihre gesamte Flächenausdehnung konstante Dicke aufweisen oder aber unterschiedliche Dicken. Darüber hinaus kann eine Schicht natürlich auch mehr als eine einzige Funktionalität aufweisen. The term "layer" refers in particular to a planar arrangement of a system of uniform functionality whose dimensions are significantly smaller in one spatial direction (thickness or height) than in the other two spatial directions defining the main extent (length and width). Such a layer can be made compact or perforated and consist of a single material or of different materials, in particular if they contribute to the uniform functionality of this layer. A layer may have a constant thickness over its entire areal extent or different thicknesses. In addition, of course, a layer may also have more than one functionality.
Der Begriff „hitzeaktivierbare Klebmasse" (in der Literatur auch als „wärmeaktivierbare Klebmasse" bezeichnet) bezeichnet Klebmassen, die durch Zufuhr thermischer Energie aktiviert werden und in diesem Zustand zur Anwendung appliziert werden. Durch Abkühlung wird die Verklebung bewirkt, wobei zwischen zwei Systemen zu unterscheiden ist: Thermoplastische hitzeaktivierbare Systeme (Schmelzklebstoffe) binden beim Abkühlen physikalisch ab (in der Regel reversibel), während hitzeaktivierbare Elastomer/Reaktivkomponenten-Systeme (Heißsiegelklebstoffe) chemisch abbinden (in der Regel irreversibel). The term "heat-activatable adhesive" (also referred to in the literature as "heat-activatable adhesive") denotes adhesives which are activated by the supply of thermal energy and applied in this state for use. By cooling, the bonding is effected, which is to distinguish between two systems: Thermoplastic heat-activated systems (hot melt adhesives) physically bind on cooling (usually reversible), while heat-reactive elastomer / reactive component systems (heat sealing adhesives) chemically set (usually irreversible ).
Dem Begriff „hitzeaktivierbare Klebmasse" steht es nicht entgegen, dass die entsprechende Klebmasse auch bei Raumtemperatur oder bei anderen Temperaturen unterhalb der Aktivierungstemperatur bereits eine gewisse Eigenklebrigkeit (Haftklebrigkeit, Selbstklebrigkeit) aufweisen kann („haftklebrig" sein kann). Diese Eigenklebrigkeit unterhalb der Aktivierungstemperatur ist aber nicht erforderlich, so dass hitzeaktivierbare Klebmasse bei Temperaturen unterhalb der Aktivierungstemperatur, insbesondere bei Raumtemperatur, auch nichtklebrig sein können.  The term "heat-activatable adhesive" does not preclude the fact that the corresponding adhesive can already have a certain inherent tack (tack, tackiness) even at room temperature or at temperatures below the activation temperature (can be "tacky"). However, this self-tackiness below the activation temperature is not necessary, so that heat-activatable adhesive compositions can also be non-sticky at temperatures below the activation temperature, in particular at room temperature.
Als unterschiedliche hitzeaktivierbare Klebmassen im Sinne dieser Schrift werden insbesondere solche hitzeaktivierbaren Klebmassen verstanden, die sich derart verhalten, dass bei einer Temperatur TDK 1 < T2 - ausgehend vom verklebten Zustand - eine der hitzeaktivierbaren Klebmassen (die erste hitzeaktivierbare Klebmasse) ihre Klebewirkung ihre Klebewirkung im Klebeverbund soweit verliert, das der Klebeverbund bezüglich der Verklebung mittels dieser hitzeaktivierbaren Klebmasse getrennt wird, während die mittels der anderen hitzeaktivierbaren Klebmasse (im weiteren als „zweite hitzeaktivierbare Klebmasse" bezeichnet) bewirkte Verklebung bei der Temperatur T2 erhalten bleibt. As a different heat-activatable adhesives in the context of this document, in particular such heat-activatable adhesives are understood, which behave such that at a temperature T DK 1 <T 2 - starting from the bonded state - one of heat-activatable adhesives (the first heat-activatable adhesive) their adhesive effect loses their adhesive effect in the adhesive composite so far that the adhesive bond is separated with respect to the adhesive bond by means of this heat-activable adhesive, while the means of the other heat-activated adhesive (hereinafter referred to as "second heat-activatable adhesive") caused bonding at the temperature T 2 is maintained.
Zur Trennung des Klebeverbundes (also zum Wiederlösen der Verklebung der beiden Substrate miteinander) bei der Temperatur T2 kann es hilfreich sein, weitere Verfahrensbedingungen vorzugeben, die den Lösevorgang unterstützen; beispielsweise zusätzlich mehr oder weniger stark trennende Kräfte (Zugkräfte, Druckkräfte oder dergleichen) einzusetzen. Für die zweite hitzeaktivierbare Klebmasse gilt dann, dass sie bei der Temperatur T2 unter der bei dem Wiederlösen des Klebeverbundes gegebenen Bedingungen, insbesondere unter Einfluss der beschriebenen Kräfte, die Verklebung mit dem Substrat, auf dem sie verklebt ist, nicht löst. For the separation of the adhesive bond (that is, for the re-bonding of the two substrates together) at the temperature T 2 , it may be helpful to specify further process conditions that support the dissolution process; For example, in addition to use more or less strong separating forces (tensile forces, compressive forces or the like). For the second heat-activatable adhesive then applies that at the temperature T 2 under the conditions given in the redissolution of the adhesive bond, in particular under the influence of the forces described, the bond with the substrate on which it is bonded, does not solve.
Die zweite hitzeaktivierbare Klebmasse kann vorteilhaft derart gewählt sein, dass sie ihrerseits die Verklebung mit dem Substrat, auf dem sie verklebt ist, bei einer dritten Temperatur T3 oberhalb der Temperatur T2 löst. The second heat-activatable adhesive can advantageously be selected such that it in turn dissolves the bond to the substrate on which it is bonded at a third temperature T 3 above the temperature T 2 .
Die Trennung der jeweiligen hitzeaktivierbaren Klebmasse von dem Substrat, auf dem sie verklebt ist, kann beispielsweise dadurch erfolgen, dass die jeweilige Klebmasse bei dieser Temperatur (T2 bzw. T3) ihre Klebkräfte verliert oder zumindest stark einbüßt, indem sie schmilzt, erweicht und/oder sich zersetzt (Dekomposition). Weitere Mechanismen des Trennvorgangs sind möglich und von dem Grundgedanken der Erfindung mit umfasst. The separation of the respective heat-activatable adhesive from the substrate on which it is bonded, for example, take place in that the respective adhesive at this temperature (T 2 or T 3 ) loses its adhesive forces or at least greatly lost by melting, softened and / or decomposes (decomposition). Further mechanisms of the separation process are possible and included in the basic idea of the invention.
In einer bevorzugten Ausgestaltung des erfindungsgemäßen Verfahrens wird die Temperatur T-i innerhalb des hitzeaktiviert verklebbaren Flächenelementees derart erzeugt, dass das elektrisch leitfähige Flächengebilde innerhalb des hitzeaktiviert verklebbaren Flächenelementes induktiv, insbesondere in einem Magnetfeld, erhitzt wird und die Wärme an die Klebmassen weitergibt. In a preferred embodiment of the method according to the invention, the temperature T-i within the heat activated bonded surface elements is generated such that the electrically conductive sheet is heated inductively within the heat activated surface element, in particular in a magnetic field, and passes the heat to the adhesives.
In einer weiteren bevorzugten Ausgestaltung wird auch die Temperatur T2, bevorzugt auch die gegebenenfalls zu erzielende Temperatur T3, durch induktive Erwärmung des elektrisch leitfähigen Flächengebildes hervorgerufen. In a further preferred embodiment, the temperature T 2 , preferably also the temperature T 3 to be achieved if appropriate, is caused by inductive heating of the electrically conductive sheet.
Im erfindungsgemäßen Verfahren werden vorteilhaft hitzeaktiviert verklebbare Flächenlemente eingesetzt, wie sie nachfolgeend näher ausgeführt werden und wie sie selbst Gegenstand der Erfindung sind. Gegenstand der Erfindung ist weiterhin ein hitzeaktiviert verklebbbares Flächenelement eingesetzt wird, das hitzeaktiviert verklebbare Flächenelement zumindest ein elektrisch leitfähiges Flächengebilde sowie zumindest zwei Schichten unterschiedlicher hitzeaktivierbarer Klebmassen umfasst, wobei sich die erste hitzeaktivierbare Klebmassenschicht im Wesentlichen auf der einen Seite des elektrisch leitfähigen Flächengebildes und die zweite hitzeaktivierbare Klebmasse im Wesentlichen auf der anderen Seite des elektrisch leitfähigen Flächengebildes befindet, wobei die hitzeaktivierbaren Klebmassen derart gewählt werden, dass sie bei einer gemeinsamen Temperatur ΤΊ eine Verklebung bewirken, und dass bei einer Temperatur TDK 1 eine der hitzeaktivierbaren Klebmassen (die erste hitzeaktivierbare Klebmasse) ihre Klebewirkung verliert, die andere (die zweite hitzeaktivierbare Klebmasse) jedoch noch nicht. In the method according to the invention heat-activated gluing surface elements are advantageously used, as they are explained in more detail below and how they themselves are the subject of the invention. The invention further provides a heat activated glued surface element is used, the heat activated bonded surface element comprises at least one electrically conductive sheet and at least two layers of different heat-activatable adhesives, wherein the first heat-activatable adhesive layer substantially on one side of the electrically conductive sheet and the second heat-activated Adhesive composition is substantially on the other side of the electrically conductive sheet, wherein the heat-activatable adhesives are chosen such that they cause bonding at a common temperature ΤΊ, and that at a temperature T DK 1 one of the heat-activatable adhesives (the first heat-activatable adhesive) their adhesive effect loses, the other (the second heat-activatable adhesive) but not yet.
Die Bezeichnung„im Wesentlichen" hat dieselbe Bedeutung wie bereits vorstehend definiert. Die Temperaturen, bei denen eine jeweilige hitzeaktivierbnare Klebmasse im Klebeverbund ihre Klebewirkung verliert, wird im Rahmen dieser Schrift auch als„Klebverlusttemperatur" bezeichnet. The term "essentially" has the same meaning as already defined above The temperatures at which a particular heat-activatable adhesive loses its adhesive effect in the adhesive bond is also referred to in this document as the "adhesive loss temperature".
Insgesamt kann das hitzeaktiviert verklebbare Flächenelement beliebig geeignet ausgebildet sein. So kann das Flächenelement zusätzlich zu den zuvor beschriebenen Schichten weitere Schichten enthalten, zum Beispiel permanente Träger oder temporäre Träger. Overall, the heat-activated bondable surface element can be designed as desired. Thus, in addition to the previously described layers, the surface element may contain further layers, for example permanent or temporary carriers.
In einer vorteilhaften Ausgestaltung des erfindungsgemäßen hitzeaktivierbaren Flächenelementes sind die Aktivierungsenergien der ersten hitzeaktivierbaren Klebmasse (TAkt1) und der zweiten Klebmasse (TAkt2) gleich oder unterscheiden sich so wenig, dass beide in einem Temperaturbereich liegen, in dem bei Erreichen, insbesondere nach Überschreitung, der höheren der beiden Aktivierungsenergien beide hitzeaktivierbaren Klebmassen ihre Klebrigkeit entfalten bzw. bereits entfaltet haben, ohne dass jedoch die Klebmasse mit der niedrigeren Aktivierungsenergie bereits ihre Klebrigkeit wieder eingebüßt hatte (etwa dadurch, dass sie zu dünnflüssig würde, sich zersetzte oder auf andere Weise nicht mehr zur Erzielung der erforderlichen Klebewirkung befähig wäre (dass also die Klebverlusttemperatur TDK einer oder beider Klebmassen bereits erreicht wäre). In an advantageous embodiment of the heat-activatable surface element according to the invention, the activation energies of the first heat-activatable adhesive (T Ak t 1 ) and the second adhesive (T Ak t 2 ) are the same or differ so little that both lie in a temperature range in which upon reaching especially after exceeding the higher of the two activating energies, both heat-activatable adhesives develop their stickiness or have already unfolded, however, without the adhesive having the lower activation energy already losing its stickiness again (eg because it would become too liquid, decomposed or on another way would no longer be able to achieve the required adhesive effect (ie that the adhesive loss temperature T DK of one or both adhesives would have already been reached).
Die erste hitzeaktivierbare Klebmasse mit der niedrigeren Klebverlusttemperatur TDK 1 kann diejenige mit der niedrigeren, aber auch diejenige mit der höheren Aktivierungstemperatur sein, sofern sich TAkt1 und TAkt2 unterscheiden. Entsprechendes gilt für die zweite hitzeaktivierbare Klebmasse mit der höheren Klebverlusttemperatur TDK 2 oder ohne Klebverlusttemperatur. The first heat-activatable adhesive having the lower adhesive loss temperature T DK 1 may be the one with the lower but also the one with the higher activation temperature, provided that T Ak 1 and T Ak 2 differ. The same applies to the second heat-activatable adhesive with the higher adhesive loss temperature T DK 2 or without adhesive loss temperature.
Die Temperatur T-i wird im erfindungsgemäßen Verfahren insbesondere derart gewählt, dass sie der höheren der beiden Aktivierungsenergien entspricht oder aber - insbesondere geringfügig - über dieser liegt, so dass beide Haftklebmassen ihre Klebrigkeit entfalten, ohne dass eine Temperatur überschritten wäre, bei der eine - oder beide - der Klebmassen ihre Klebrigkeit wieder einbüßen würden. In the process according to the invention, the temperature Ti is chosen in particular such that it corresponds to the higher of the two activation energies or-above all-above this, so that both pressure-sensitive adhesives develop their stickiness without exceeding a temperature at which one or both - The adhesives would lose their stickiness again.
Die Temperaturen, bei der die hitzeaktivierbaren Klebmassen ihre Klebrigkeit einbüßen (den Erhalt des Klebeverbundes nicht mehr zu bewirken vermögen; Klebverlusttemperaturen TDK 1 der ersten hitzeaktivierbaren Klebmasse, TDK 2 der zweiten hitzeaktivierbaren Klebmasse) unterscheiden sich dabei bevorzugt derart signifikant, dass verfahrenstechnisch eine Temperatur T2 (oder ein Temperaturbereich T2) realisiert werden kann, dass die Verklebung des ersten Substrats mit der ersten hitzeaktivierbaren Klebmasse mit der niedrigeren Klebverlusttemperatur TDK 1 gelöst wird, während die Verklebung des zweiten Substrats mit der zweiten hitzeaktivierbaren Klebmasse mit der höheren (oder ohne existierende) Klebverlusttemperatur TDK 2 (noch) erhalten bleibt. The temperatures at which the heat-activatable adhesives lose their stickiness (can no longer achieve the retention of the adhesive bond; adhesive loss temperatures T DK 1 of the first heat-activatable adhesive, T DK 2 of the second heat-activable adhesive) preferably differ so significantly that in terms of process technology a temperature T 2 (or a temperature range T 2 ) can be realized that the bonding of the first substrate with the first heat-activatable adhesive having the lower adhesive loss temperature T DK 1 is solved, while the bonding of the second substrate with the second heat-activatable adhesive with the higher (or without existing) adhesive loss temperature T DK 2 (still) is maintained.
Die Temperaturen
Figure imgf000013_0001
TAkt 2, TDK 1 und/oder TDK 2 können scharf definierte Temperaturen sein, da es sich bei HaftKlebmassen jedoch um Polymere handelt, bei denen Phasenumwandlungen bzw. andere physikalische, chemische und/oder physikochemische Prozesse innerhalb von Temperaturbereichen stattfinden, sollen derartige Temperaturbereiche mit umfasst sein.
The temperatures
Figure imgf000013_0001
T Akt 2 , T DK 1 and / or T DK 2 can be sharply defined temperatures, since adhesive adhesives are polymers in which phase transformations or other physical, chemical and / or physicochemical processes take place within temperature ranges Temperature ranges to be included.
Die angegebene Temperatur T bezeichnet dann insbesondere die Temperatur innerhalb des jeweiligen Temperaturbereiches, bei dem der entsprechende Prozess (Hitzeaktivierung, Schmelzen, Erweichen, Zersetzung, etc) wesentlich erfolgt ist, so dass der beschrieben Erfolg im Verfahren (also die Verklebung bzw. das Wiederlösen) eintritt.  The specified temperature T then designates in particular the temperature within the respective temperature range at which the corresponding process (heat activation, melting, softening, decomposition, etc.) has essentially taken place, so that the described success in the process (ie the bonding or the redissolving) entry.
Die Verfahrenstemperatur T-i bezeichnet eine Temperatur gleich oder oberhalb der Aktivierungstemperaturen TAkt1 und TAk 2 der hitzeaktivierbaren Klebmassen. The process temperature Ti denotes a temperature equal to or above the activation temperatures T A kt 1 and T Ak 2 of the heat-activatable adhesives.
Die Verfahrenstemperatur T2 bezeichnet eine Temperatur gleich oder oberhalb der Klebverlusttemperatur TDK 1 der ersten hitzeaktivierbaren Klebmasse; sofern auch die zweite hitzeaktivierbare Klebmasse eine Klebverlusttemperatur TDK 2 besitzt, liegt T2 unterhalt TDK 2. Die Verfahrenstemperatur T3 bezeichnet eine Temperatur gleich oder oberhalb der Klebverlusttemperatur TDK 2*. Wie bereist dargelegt kommen als Klebverlusttemperaturen der hitzeaktivierbaren Klebmassen unabhängig von der jeweils anderen hitzeaktivierbaren Klebmasse insbesondere deren jeweilige Schmelztemperatur, Erweichungstemperatur, Zersetzungstemperatur oder ähnliches in Frage; wobei der Klebeverlust beider hitzeaktivierbaren Klebmassen natürlich auch auf denselben Effekt zurückzuführen sein kann. The process temperature T 2 denotes a temperature equal to or above the adhesive loss temperature T DK 1 of the first heat-activatable adhesive; If the second heat-activatable adhesive also has an adhesive loss temperature T DK 2 , T 2 is T DK 2 . The process temperature T 3 designates a temperature equal to or above the adhesive loss temperature T DK 2 * . As already stated, the heat-activatable adhesives having adhesive loss temperatures, independently of the respective other heat-activatable adhesive, are in particular their respective melting temperature, softening temperature, decomposition temperature or the like; Of course, the adhesion loss of both heat-activatable adhesives can also be due to the same effect.
Eine vorteilhafte Ausführungsform der erfindungsgemäßen Klebebänder betrifft ein hitzeaktiviert verklebbares Flächenelement, umfassend zumindest ein elektrisch leitfähiges Flächengebilde sowie zumindest jeweils eine Schicht einer hitzeaktivierbaren Klebmassen auf den beiden Seiten des elektrisch leitfähigen Flächengebildes, wobei sich die beiden hitzeaktivierbaren Klebmassen unterscheiden, und wobei die Aktivierungstemperaturen zur Erzielung der Klebeeigenschaften der hitzeaktivierbaren Klebmassen sich weniger unterscheiden als deren Klebverlusttemperaturen, insbesondere als deren Schmelztemperaturen und/oder als deren Zersetzungstemperaturen. An advantageous embodiment of the adhesive tapes according to the invention relates to a heat-activated adhesive surface element comprising at least one electrically conductive sheet and at least one layer of heat-activatable adhesives on the two sides of the electrically conductive sheet, wherein the two heat-sensitive adhesives differ, and wherein the activation temperatures to achieve Adhesive properties of the heat-activatable adhesives differ less than their adhesive loss temperatures, in particular as their melting temperatures and / or as their decomposition temperatures.
Die erfindungsgemäßen hitzeaktiviert verklebbaren Flächenelemente und das erfindungsgemäße Verfahren sind insbesondere geeignet zur Verklebungen zwischen zumindest zwei gleichen oder verschiedenen elektrisch nichtleitenden Materialien (Substrate im Sinne des oben verwendeten Begriffes), insbesondere solchen mit Wärmeleitungskoeffizienten von jeweils weniger als 5 W/mK, besonders bevorzugt in elektronischen Geräten. The heat-activated bondable surface elements according to the invention and the method according to the invention are particularly suitable for bonding between at least two identical or different electrically non-conductive materials (substrates in the sense of the term used above), in particular those with heat conduction coefficients of less than 5 W / mK, particularly preferably in electronic Devices.
Erfindungsgemäß kann die Verklebung in einem für beide gleichen Temperaturbereich durchgeführt werden, indem beide Klebmassen die vollständige Verklebungsfeestigkeit erzeilen (ohne dass eines der Materialien nicht seine vollständige Verklebungsfestigkeit erreicht, z.B. durch unvollständiges Aushärten oder Aufschmelzen). Vorteilhaft wird keines der beteiligten materilaien (Substrate, Klebmassen) durch zu hohe Temperatur geschädigt wird. According to the invention, the bonding can be carried out in a temperature range which is the same for both in that both adhesives achieve the complete bond strength (without one of the materials not achieving its complete bond strength, for example by incomplete curing or melting). Advantageously, none of the materilaien involved (substrates, adhesives) is damaged by excessive temperature.
Durch die Wahl der Temperatur T2 beim Lösen der Verbindung, insbesondere einer niedrigeren Temperatur, kann zudem sicher vorherbestimmt werden, auf welchem Fügepartner das elektrisch leitfähige Flächengebilde haften bleibt. Dies ist für den Recyclingvorgang der insbesondere elektronischen Geräte vorteilhaft, insbesondere füpr eine saubere Materialsortierung. By choosing the temperature T 2 when releasing the connection, in particular a lower temperature, can also be safely predicted on which joining partner sticks the electrically conductive sheet. This is advantageous for the recycling process of the particular electronic devices, in particular for a clean material sorting.
Überraschend ist es gelungen, trotz zweier unterschiedlicher Klebersysteme und in dem verklebbaren Flächenelement vorliegenden zusätzlichen Grenzschichten an dem elektrisch leitfähigen Flächengebilde Verklebungsfestigkeiten zu erreichen, die sonst nur mit Monosystemen, wie z.B. partikelgefüllten Klebstoffen, die homogen in der Klebefuge vorliegen, erreicht werden. It has surprisingly been possible, despite two different adhesive systems and in the adhesive surface element present additional boundary layers on the electric Conductive fabrics to achieve bond strengths, which are otherwise only with mono systems, such as particle-filled adhesives, which are present homogeneously in the adhesive joint, can be achieved.
In einer besonders vorteilhaften Ausführung weist das hitzeaktiviert verklebbare Flächenelement eine Dicke von weniger als 70 μηη, insbesondere von weniger als 50 μηη, ganz besonders von weniger als 30 μηη auf, da hiermit besonders dünne Klebverbindungen hergestellt werden können.. In a particularly advantageous embodiment, the heat-activated glued surface element has a thickness of less than 70 μηη, in particular less than 50 μηη, especially of less than 30 μηη, as this particularly thin glued connections can be made.
Von der Erfindung umfasst ist ein Verfahren zur Herstellung einer Klebeverbindung, bei dem ein erfindungsgemäßes hitzeaktiviert verklebbares Flächenelement insbesondere in der Geometrie der herzustellenden Klebeverbindung (z.B. als Zuschnitt oder Stanzling) zur Verfügung gestellt wird, The invention encompasses a method for producing an adhesive bond, in which a heat-activated, bondable surface element according to the invention is made available, in particular, in the geometry of the adhesive bond to be produced (for example as a blank or diecut),
• dieses Flächenelement in die Klebefuge appliziert wird,  • this surface element is applied in the glue joint,
• die Klebefuge mit Druck beaufschlagt wird, wobei der Druck durch eine Pressvorrichtung aufgebracht wird, von der zumindest ein Presswerkzeug eine Vorrichtung zur Erzeugung eines magnetischen Wechselfeldes enthält,  The pressure is applied to the adhesive joint, the pressure being applied by a pressing device, of which at least one pressing tool contains a device for generating an alternating magnetic field,
• und das Flächenelement mittels Induktion auf eine Temperatur erwärmt wird, bei der beide Klebersysteme aktiviert werden  • and the surface element is heated by induction to a temperature at which both adhesive systems are activated
Weiterhin von der erfindung umfasst ist ein Verfahren zum Lösen einer Klebverbindung, insbesondere in Folge des zuvor dargestellten Verfahrens zur Herstellung einer klebeverbindung, bei dem eine mit einem erfindungsgemäßen hitzeaktiviert verklebbaren Flächenelement Klebeband hergestellte Klebeverbindung mittels Induktion erwärmt wird, dadurch gekennzeichnet, dass Furthermore, the invention comprises a method for releasing an adhesive bond, in particular as a consequence of the previously described method for producing a bonded joint, in which an adhesive bond produced with a heat-activated adhesive surface element adhesive tape according to the invention is heated by means of induction, characterized in that
• die niedrigere der für die beiden hitzeaktivierbaren Klebemasen zum Herabsetzen der Adhäsion und/oder der Kohäsion erforderlichen Temperaturen nicht wesentlich überschritten wird.  • the lower temperature required for the two heat-activatable adhesives to reduce adhesion and / or cohesion is not significantly exceeded.
Die Erwärmung des erfindungsgemäßen Flächenelementes lässt sich unter Verwendung eines zum induktiven Erwärmen üblichen Induktionsheizmittel (Induktors) durchführen. Als Induktionsheizungsmittel (Induktor) kommen alle üblichen und geeigneten Anordnungen in Frage, also etwa von einem elektrischen Wechselstrom durchflossene Spulen, Leiterschleifen oder Leiter, die infolge des hindurchfließenden Stroms ein Magnet- Wechselfeld geeigneter Stärke erzeugen. So kann die zum Erwärmen erforderliche Magnetfeldstärke durch eine Spulenanordnung von entsprechender Wicklungszahl und Spulenlänge bereit gestellt werden, die von einem entsprechenden Strom durchflössen ist, beispielsweise als Punktinduktor. Diese kann ohne ferromagnetischen Kern ausgebildet sein oder aber einen Kern aufweisen, beispielsweise aus Eisen oder gepresstem Ferritpulver. Der Vorverbund kann dem so erzeugten Magnetfeld direkt ausgesetzt sein. Alternativ ist es natürlich auch möglich, obige Spulanordnung als Primärwicklung auf der Primärseite eines Magnetfeldübertragers (Transformator) anzuordnen, auf dessen Sekundärseite eine Sekundärwicklung einen entsprechend höheren Strom bereitstellt. Dadurch kann die in der unmittelbaren Nähe des Vorverbunds angeordnete eigentliche Erregerspule infolge des höheren Stroms eine geringere Zahl an Windungen aufweisen, ohne dass dadurch die Feldstärke des Magnet-Wechselfeldes verringert wird. The heating of the surface element according to the invention can be carried out using a customary for inductive heating Induktionsheizmittel (inductor). Suitable induction heating means (inductor) are all customary and suitable arrangements, that is to say coils, conductor loops or conductors through which an electric alternating current flows, which generate a magnetic alternating field of suitable strength as a result of the current flowing through it. Thus, the magnetic field strength required for heating can be provided by a coil arrangement of corresponding winding number and coil length, which is traversed by a corresponding current, for example as a point inductor. This may be formed without ferromagnetic core or have a core, for example, iron or pressed ferrite powder. The precombustion can be directly exposed to the magnetic field thus generated. Alternatively, it is of course also possible to arrange the above coil arrangement as a primary winding on the primary side of a magnetic field transformer (transformer), on whose secondary side a secondary winding provides a correspondingly higher current. As a result, the actual exciter coil arranged in the immediate vicinity of the preassembly can have a smaller number of turns due to the higher current, without thereby reducing the field strength of the alternating magnetic field.
Für den Fall, dass der Vorverbund während des induktiven Erwärmens mit einem Pressdruck beaufschlagt wird, ist hierfür zusätzlich eine Pressvorrichtung erforderlich. Als Pressvorrichtung können alle zum Ausüben eines Pressdrucks geeigneten Vorrichtungen eingesetzt werden, zum Beispiel diskontinuierlich arbeitende Pressmaschinen wie etwa eine Pneumatik- oder Hydraulikpresse, eine Exzenterpresse, eine Kurbelpresse, eine Kniehebelpresse, eine Spindelpresse oder dergleichen, oder auch kontinuierlich arbeitende Pressmaschinen wie etwa eine Presswalze. Die Vorrichtung kann als separate Einheit vorgesehen sein oder aber mit dem Induktor verbunden vorliegen. Bevorzugt kommt etwa eine Vorrichtung zum Einsatz, die als erstes Presswerkzeug zumindest ein Pressstempelelement enthält, das zudem ein Induktionsheizungsmittel aufweist. Dadurch kann das Induktionsfeld sehr nah an die zu bildende Verklebungsstelle herangeführt werden und somit auch räumlich auf die Fläche dieser Verklebungsstelle begrenzt werden. In the event that the pre-bond is subjected to a pressing pressure during the inductive heating, a pressing device is additionally required for this purpose. As the press apparatus, there may be used any apparatus suitable for applying a pressing pressure, for example, batch type press machines such as a pneumatic or hydraulic press, an eccentric press, a crank press, a toggle press, a screw press or the like, or also continuous press machines such as a press roller. The device may be provided as a separate unit or connected to the inductor. Preferably, for example, a device is used which, as the first pressing tool, contains at least one pressing punch element which additionally has an induction heating means. As a result, the induction field can be brought very close to the bonding point to be formed and thus also limited spatially to the surface of this bonding point.
Vorteilhaft können für die induktive Erwärmung folgende Parameter gewählt werden: Advantageously, the following parameters can be selected for inductive heating:
- eine Frequenz zwischen 1 und 200 kHz, da bei niedrigen Frequenzen höhere Eindringtiefen erzielt werden können und eine bessere Kontrolle der Aufheizrate möglich ist. Besonders bevorzugt werden bei dem Verfahren Frequenzen von 1 bis 40 kHz, insbesondere von 1 bis 15 kHz eingesetzt, da hierbei die wirksame Eindringtiefe des Magnetfelds weiter vergrößert ist.  - A frequency between 1 and 200 kHz, because at low frequencies higher penetration depths can be achieved and a better control of the heating rate is possible. Frequencies of 1 to 40 kHz, in particular of 1 to 15 kHz are particularly preferably used in the method, since in this case the effective penetration depth of the magnetic field is further increased.
- Durchführung der Aufheizung in einer Zeit von weniger als 20 s auf eine Temperatur von mehr als 70 °C.  - Carry out the heating in a time of less than 20 s to a temperature of more than 70 ° C.
Besonders vorteilhaft wird das Verfahren verwendet, wenn die die erwärmte Fläche kleiner als 5 cm2 ist. Überraschend kann mit dem Verfahren ein unkontrolliertes Aufschmelzen der dann sehr filigranen Verklebungssubstrate vermieden werden. Besonders vorteilhaft wird das Verfahren weiterhin verwendet, wenn die Klebefuge als eine nicht geschlossene Fläche ausgebildet ist. Darunter sind einerseits von Aussparungen und/oder durchbrochene Flächen zu verstehen, andererseits auch im Wesentlichen aus linienförmigen Elementen zusammengesetzte Flächen, z.B. eine Kammstruktur, bei denen einzelne Elemente ein Aspektverhältnis (Länge zu Breite) von mehr als 2 aufweisen. Particularly advantageously, the method is used when the heated area is less than 5 cm 2 . Surprisingly, the method avoids an uncontrolled melting of the then very filigree bonding substrates. Particularly advantageously, the method is further used when the adhesive joint is formed as a non-closed surface. These are on the one hand to be understood as recesses and / or perforated surfaces, on the other hand also substantially composed of line-shaped elements surfaces, such as a comb structure in which individual elements have an aspect ratio (length to width) of more than 2.
In einer besonders vorteilhaften Ausführung des Verfahrens wird beim Erwärmen ein Pressdruck ausgeübt, der mehr als 0,2 MPa beträgt. Hiermit kann eine Blasenbildung durch desorbierende oder in einer chemischen Reaktion entstehende Gase, insbesondere durch Wasserdampf, vermieden werden. Bevorzugt für hohe Vernetzungstemperaturen ist ein Druck von mehr als 0,5 MPa. In a particularly advantageous embodiment of the method, a pressing pressure is exerted on heating, which is more than 0.2 MPa. This can be a blistering by desorbing or resulting in a chemical reaction gases, in particular by steam, avoided. Preferred for high crosslinking temperatures is a pressure of more than 0.5 MPa.
In einer weitern, besonders vorteilhaften Ausführung des Verfahrens beträgt der Druck hingegen weniger als 0,2 MPa, da hiermit ein Ausquetschen von Kleber, insbesondere von thermoplastischem Kleber, aus der Klebefuge vermieden werden kann. In a further, particularly advantageous embodiment of the method, the pressure, however, is less than 0.2 MPa, since this squeezing of adhesive, in particular thermoplastic adhesive, can be avoided from the adhesive joint.
In einer besonders vorteilhaften Ausführung beträgt die Aufheizrate nicht mehr als 200 °C/s, , insbesondere nicht mehr als 100 °C/s, da bei höheren Aufheizraten die Gefahr der Materialschädigung der hitzeaktivierbaren Klebmasse oder des unkontrollierten Aufschmelzens bzw. einer thermischen Schädigung des Substrats groß ist. Eine solche Begrenzung der Aufheizrate kann z.B. mit der Verwendung von weniger elektrisch leitfähigen Metallen (z.B. Aluminium statt Kupfer oder Stahl statt Aluminium) erreicht werden. Ein weiteres technisches Mittel zur Begrenzung der Aufheizrate ist die Verwendung von durchbrochenen metallischen Flächengebilden, z.B. von Streckmetall). In a particularly advantageous embodiment, the heating rate is not more than 200 ° C / s, in particular not more than 100 ° C / s, since at higher heating rates, the risk of material damage to the heat-activated adhesive or the uncontrolled melting or thermal damage to the substrate is great. Such a limitation of the heating rate may e.g. with the use of less electrically conductive metals (e.g., aluminum instead of copper or steel instead of aluminum). Another technical means of limiting the heating rate is the use of openwork metallic sheets, e.g. of expanded metal).
In einer weiteren vorteilhaften Ausführung des Verfahrens wird nach dem Erwärmen des Flächenelementes der Druck aufrechterhalten, um eine Verfestigung der Klebefuge durch physikalische oder chemische Mechanismen zu ermöglichen. Vorteilhaft ist es auch, diese Nachpresszeit in einer zweiten Pressvorrichtung durchzuführen, die keinen Induktor mehr enthalten muss, um damit die Zykluszeit zu reduzieren. In a further advantageous embodiment of the method, the pressure is maintained after the heating of the surface element, in order to allow solidification of the adhesive joint by physical or chemical mechanisms. It is also advantageous to carry out this repressing time in a second pressing device, which no longer has to contain an inductor in order to reduce the cycle time.
In einer weiteren vorteilhaften Ausführung des Verfahrens wird in zumindest einem Teil dieser Nachpresszeit auch eine weitere Induktionserwärmung des Klebebands durchgeführt, da hiermit vorteilhaft die Temperatur in der Klebefuge aufrechterhalten werden kann. Vorteilhaft wird diese Nacherwärmung mit einer geringeren Aufheizrate durchgeführt, als die Ersterwärmung. Dadurch, dass das Klebeband bevorzugt in der Geometrie der Verklebungsfläche zur Verfügung gestellt wird, wird sichergestellt, dass das Aufheizen nur in den für die Verklebung benötigten Bereichen stattfindet. Die Gefahr von thermischen Schädigungen ist somit verringert. Die Herstellung der Geometrie kann durch alle dem Fachmann geläufigen Verfahren wie z.B. Schneiden, Stanzen, Laserschneiden, Wasserstrahlschneiden erfolgen. In a further advantageous embodiment of the method, a further induction heating of the adhesive tape is also carried out in at least part of this repressing time, since this advantageously allows the temperature in the glue joint to be maintained. Advantageously, this reheating is carried out at a lower heating rate than the first heating. The fact that the adhesive tape is preferably provided in the geometry of the bond area ensures that the heating takes place only in the areas required for the bonding. The risk of thermal damage is thus reduced. The production of the geometry can be carried out by all methods familiar to the person skilled in the art, such as, for example, cutting, punching, laser cutting, water jet cutting.
Vorteil des Verfahrens ist es weiterhin, dass der Induktor in zumindest einem der Presswerkzeuge integriert ist, da hiermit das Induktionsfeld sehr nah an die Verklebungsstelle herangebracht werden kann und auch räumlich auf diese begrenzt werden kann. Another advantage of the method is that the inductor is integrated in at least one of the pressing tools, since hereby the induction field can be brought very close to the bonding site and also spatially limited to it.
Hitzeaktivierbare Klebmassen Heat-activated adhesives
Als hitzeaktivierbare Klebmassen können insbesondere Schmelzklebstoffe, reaktive Klebstoffe oder reaktive Schmelzklebstoffe eingesetzt werden. In particular, hot melt adhesives, reactive adhesives or reactive hot melt adhesives can be used as the heat-activatable adhesives.
Bevorzugt besitzt die erste hitzeaktivierbare Klebmasse eine Klebverlusttemperatur (TDK 1), die zwischen 10 und 20 °C, bevorzugt zwischen 20 und 50 °C, besonders bevorzugt zumindest 50 °C oberhalb der Aktivierungstemperatur (TAkt2*) der zweiten hitzeaktivierbaren Klebmasse liegt. Damit ist sichergestellt, dass innerhalb eines Aufheizzyklusses beide Klebmassen sicher aktiviert werden können, ohne bereits für den ersten Kleber den Ablösemechanismus (die Dekomposition) zu aktivieren. Bei einer Differenz von 10 - 20 °C ist die zum Trennen der Verbindung notwendige Temperatur relativ niedrig, so dass Aufheizzeit und/oder Energie gespart werden können. The first heat-activatable adhesive preferably has an adhesive loss temperature (T DK 1 ) of between 10 and 20 ° C., preferably between 20 and 50 ° C., more preferably at least 50 ° C. above the activation temperature (T Ak 2 * ) of the second heat-activatable adhesive lies. This ensures that both adhesives can be safely activated within a heat-up cycle without activating the release mechanism (the decomposition) for the first adhesive. With a difference of 10 - 20 ° C, the temperature necessary for disconnecting the connection is relatively low, so that heating time and / or energy can be saved.
Bei einer Differenz der vorstehend genanten Temperaturen (TDK 1, EAkt2) von mehr als 50 °C ist das Verfahren sehr sicher, da in der Temperaturführung beim Verkleben größere Toleranzen zugelassen werden. With a difference of the above-mentioned temperatures (T DK 1 , E Ak t 2 ) of more than 50 ° C, the process is very safe, as in the temperature control during bonding larger tolerances are allowed.
Der Bereich einer Temperaturdifferenz von 20 °C bis 50 °C ist vorteilhafter Kompromiss zwischen beiden Varianten.  The range of a temperature difference of 20 ° C to 50 ° C is an advantageous compromise between the two variants.
In einer besonders bevorzugten Ausführung ist die erste hitzeaktivierbare Klebmasse ein reaktiven Klebstoff oder umfasst einen solchen oder ist ein reaktiver Schmelzklebstoff oder umfasst einen solchen, und/oder die zweite hitzeaktivierbare Klebmasse ist ein Schmelzklebstoff oder umfasst einen solchen, wobei sehr bevorzugt die Schmelztemperatur des Schmelzklebstoff kleiner als die Zersetzungstemperatur (Dekompositionstemperatur) des reaktiven Systems gewählt ist. Dadurch kann ein Lösen der Klebverbindung ohne chemische Zersetzung (Dekomposition) und damit möglicher Gefährdung durch dabei entstehende Gase oder andere Zersetzungsprodukte erfolgen. In a particularly preferred embodiment, the first heat-activatable adhesive is or comprises a reactive adhesive or a reactive hot melt adhesive, and / or the second heat-activable adhesive is or comprises a hot melt adhesive, very preferably the melting temperature of the hot melt adhesive being smaller as the decomposition temperature (decomposition temperature) of the reactive system is selected. This can be done a release of the adhesive bond without chemical decomposition (decomposition) and thus possible danger from the resulting gases or other decomposition products.
In einer weiteren bevorzugten Ausführung sind zumindest der einen hitzeaktivierbaren Klebmasse Anteile von zumindest einem Material beigesetzt, die die Dekomposition beschleunigen oder die bevorzugt dekompositionieren und so die Klebverbindung schwächen und zur Lösung derselben führen. Beispiele hierfür sind dem Fachmann bekannt und z.B. in der US 5,272,216 dargestellt. Die entsprechenden dort dargestellten Materialien seien in den Offenbarungsumfang der vorliegenden Schrift explizit eingeschlossen. In a further preferred embodiment, at least one of the heat-activatable adhesives contains fractions of at least one material which accelerate the decomposition or which preferably decompose and thus weaken the adhesive bond and lead to the solution thereof. Examples of these are known to those skilled in the art and e.g. shown in US 5,272,216. The corresponding materials shown there are explicitly included in the disclosure of the present specification.
Als die zumindest eine hitzeaktiviert verklebbare Klebmasse können grundsätzlich alle üblichen hitzeaktiviert verklebbaren Klebmassensysteme zum Einsatz gelangen. Hitzeaktiviert verklebbare Klebmassen lassen sich grundsätzlich in zwei Kategorien einordnen: thermoplastische hitzeaktiviert verklebbare Klebmassen (Schmelzklebstoffe) und reaktive hitzeaktiviert verklebbare Klebmassen (Reaktivklebstoffe). Diese Einteilung enthält auch solche Klebmassen, die sich beiden Kategorien zuordnen lassen, nämlich reaktive thermoplastische hitzeaktiviert verklebbare Klebmassen (reaktive Schmelzklebstoffe). In principle, all conventional heat-activated adhesive mass adhesive systems can be used as the at least one heat-activated adhesive composition. Heat-activated adhesives which can be bonded together can basically be classified into two categories: thermoplastic heat-activated adhesives (hot-melt adhesives) and reactive heat-activated adhesives (reactive adhesives). This classification also includes those adhesives which can be assigned to both categories, namely reactive thermoplastic heat activated adhesives (reactive hot melt adhesives).
Thermoplastische Klebmassen basieren auf Polymeren, die bei einem Erwärmen reversibel erweichen und während des Erkaltens wieder erstarren. Im Gegensatz dazu enthalten reaktive hitzeaktiviert verklebbare Klebmassen reaktive Komponenten. Letztere Bestandteile werden auch als "Reaktivharze" bezeichnet, in denen durch das Erwärmen ein Vernetzungsprozess eingeleitet wird, der nach Beendigen der Vernetzungsreaktion eine dauerhafte stabile Verbindung auch unter Druck gewährleistet. Bevorzugt enthalten derartige thermoplastische Klebmassen auch elastische Komponenten, zum Beispiel synthetische Nitrilkautschuke. Derartige elastische Komponenten verleihen der hitzeaktiviert verklebbaren Klebmasse infolge ihrer hohen Fließviskosität eine auch unter Druck besonders hohe Dimensionsstabilität. Thermoplastic adhesives are based on polymers that soften reversibly when heated and solidify again during cooling. In contrast, reactive heat activated adhesives contain reactive components. The latter constituents are also referred to as "reactive resins" in which the heating initiates a crosslinking process which, after completion of the crosslinking reaction, ensures a permanent stable compound even under pressure. Such thermoplastic adhesives preferably also contain elastic components, for example synthetic nitrile rubbers. Due to their high flow viscosity, such elastic components impart to the heat-activated adhesive composition a particularly high dimensional stability even under pressure.
Im Folgenden sind rein exemplarisch einige typische Systeme hitzeaktiviert verklebbarer Klebmassen beschrieben, die sich im Zusammenhang mit der vorliegenden Erfindung als besonders vorteilhaft herausgestellt haben. Below, by way of example only, some typical systems of heat-activated adhesive compositions which have been found to be particularly advantageous in connection with the present invention are described.
Eine thermoplastische hitzeaktiviert verklebbare Klebmasse enthält also ein thermoplastisches Basispolymer. Dieses weist bereits bei geringem Anpressdruck ein gutes Fließverhalten auf, so dass sich die für die Haltbarkeit einer dauerhaften Verklebung relevante finale Klebkraft innerhalb kurzer Anpresszeit einstellt und daher ein schnelles Verkleben auch auf rauem oder anderweitig kritischem Untergrund möglich ist. Als thermoplastische hitzeaktiviert verklebbare Klebmassen können alle aus dem Stand der Technik bekannten thermoplastischen Klebmassen verwendet werden. A thermoplastic heat-activated adhesive composition thus contains a thermoplastic base polymer. This has a good flow behavior even at low contact pressure, so that the for the durability of a permanent bond setting relevant final bond strength within a short contact time and therefore rapid bonding is also possible on rough or otherwise critical substrates. Thermoplastic adhesives which can be adhesively bonded to form a heat-activated adhesive can be any of the thermoplastic adhesives known from the prior art.
Geeignet sind beispielsweise solche hitzeaktivierbaren Klebmassen, wie sie in der DE 10 2006 042 816 A1 beschrieben sind, ohne sich durch diese Angaben beschränken zu wollen. Suitable examples are those heat-activatable adhesives, as described in DE 10 2006 042 816 A1, without wishing to be limited by this information.
Exemplarische Zusammensetzungen sind etwa in EP 1 475 424 A1 beschrieben. So kann die thermoplastische Klebmasse beispielsweise eine oder mehrere der folgenden Komponenten enthalten oder sogar aus diesen bestehen: Polyolefine, Ethylen-Vinylacetat- Copolymere, Ethylen-Ethylacrylat-Copolymere, Polyamide, Polyester, Polyurethane oder Butadien-Styrol-Blockcopolymere. Bevorzugt kommen etwa die in Absatz [0027] von EP 1 475 424 A1 aufgeführten thermoplastischen Klebmassen zum Einsatz. Weitere thermoplastische Klebmassen, die insbesondere für spezielle Einsatzgebiete wie zum Beispiel das Verkleben von Verklebungssubstraten aus Glas besonders geeignet sind, sind in EP 1 95 60 63 A2 beschrieben. Bevorzugt werden thermoplastische Klebmassen verwendet, deren Schmelzviskosität durch rheologische Additive heraufgesetzt ist, beispielsweise durch Zusatz von pyrogenen Kieselsäuren, Ruß, Kohlenstoff-Nanoröhren und/oder weiteren Polymeren als Abmischkomponenten. Exemplary compositions are described, for example, in EP 1 475 424 A1. Thus, the thermoplastic adhesive may for example contain or even consist of one or more of the following components: polyolefins, ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, polyamides, polyesters, polyurethanes or butadiene-styrene block copolymers. Preferably, for example, the thermoplastic adhesives listed in paragraph [0027] of EP 1 475 424 A1 are used. Other thermoplastic adhesives which are particularly suitable for special applications, such as the bonding of glass adhesion substrates, are described in EP 1 95 60 63 A2. Preference is given to using thermoplastic adhesives whose melt viscosity is increased by rheological additives, for example by addition of pyrogenic silicas, carbon black, carbon nanotubes and / or further polymers as blending components.
Eine reaktive hitzeaktiviert verklebbare Klebmasse weist hingegen vorteilhafterweise ein elastomeres Basispolymer und ein Modifikationsharz auf, wobei das Modifikationsharz ein Klebharz und/oder ein Reaktivharz umfasst. Infolge der Verwendung eines elastomeren Basispolymers ist es möglich, Klebeschichten mit hervorragender Dimensionsstabilität zu erhalten. Als reaktive hitzeaktiviert verklebbare Klebmassen können entsprechend den jeweiligen konkreten Anwendungen alle aus dem Stand der Technik bekannten hitzeaktiviert verklebbaren Klebmassen eingesetzt werden. On the other hand, a reactive heat-activated adhesive composition advantageously comprises an elastomeric base polymer and a modification resin, wherein the modification resin comprises an adhesive resin and / or a reactive resin. Due to the use of an elastomeric base polymer, it is possible to obtain adhesive layers having excellent dimensional stability. As reactive heat-activated adhesive compositions can be used according to the respective specific applications, all known from the prior art heat-activated adhesive compositions bondable.
Dies beinhaltet zum Beispiel auch reaktive hitzeaktiviert verklebbare Folien auf Basis von Nitrilkautschuken oder deren Derivaten wie etwa Nitrilbutadienkautschuke oder Mischungen (Blends) dieser Basispolymere, die zusätzlich Reaktivharze wie etwa Phenolharze enthalten; ein derartiges Produkt ist etwa unter der Bezeichnung tesa 8401 kommerziell erhältlich. Der Nitrilkautschuk verleiht der hitzeaktiviert verklebbaren Folie infolge seiner hohen Fliessviskosität eine ausgeprägte Dimensionsstabilität, wodurch sich nach Durchführen einer Vernetzungsreaktion hohe Klebkräfte auf Kunststoffoberflächen realisieren lassen. Natürlich lassen sich auch andere reaktive hitzeaktiviert verklebbare Klebmassen einsetzen wie etwa Klebmassen, die zu einem Masseanteil von 50 bis 95 Gew.-% ein verklebbares Polymer und zu einem Masseanteil von 5 bis 50 Gew.-% ein Epoxidharz oder eine Mischung aus mehreren Epoxidharzen enthalten. Das verklebbare Polymer enthält hierbei vorteilhafterweise zu 40 bis 94 Gew.-% Acrylsäureverbindungen und/oder Methacrylsäureverbindungen der allgemeinen Formel CH2=C(R1)(COOR2) (R1 stellt hierbei einen Rest dar, der ausgewählt ist aus der Gruppe umfassend H und CH3, und R2 stellt einen Rest dar, der ausgewählt ist aus der Gruppe umfassend H und lineare oder verzweigte Alkylketten mit 1 bis 30 Kohlenstoffatomen), zu 5 bis 30 Gew.-% ein erstes copolymerisierbares Vinylmonomer, das zumindest eine Säuregruppe aufweist, insbesondere eine Carbonsäuregruppe und/oder Sulfonsäuregruppe und/oder Phosphonsäuregruppe, zu 1 bis 10 Gew.-% ein zweites copolymerisierbares Vinylmonomer, das zumindest eine Epoxidgruppe oder eine Säureanhydridfunktion aufweist, und zu 0 bis 20 Gew.-% ein drittes copolymerisierbares Vinylmonomer, das zumindest eine funktionelle Gruppe aufweist, die sich von der funktionellen Gruppe des ersten copolymerisierbaren Vinylmonomers und von der funktionellen Gruppe des zweiten copolymerisierbaren Vinylmonomers unterscheidet. Eine derartige Klebmasse ermöglicht ein Verkleben mit einer schnellen Aktivierung, bei der innerhalb kurzer Zeit bereits die finale Klebkraft erreicht wird, so dass hierdurch insgesamt eine gut haftende Verbindung auf unpolarem Untergrund gewährleistet ist. This includes, for example, reactive heat activated bonded films based on nitrile rubbers or their derivatives such as nitrile butadiene rubbers or mixtures (blends) of these base polymers, which additionally contain reactive resins such as phenolic resins; such a product is commercially available as tesa 8401 approximately. The nitrile rubber gives the heat-activated bondable film due to its high flow viscosity a pronounced dimensional stability, which can be achieved after performing a crosslinking reaction high bond strengths on plastic surfaces. Of course, it is also possible to use other reactive heat-activated adhesives which can be bonded, such as adhesives containing from 50 to 95% by weight of a tacky polymer and from 5 to 50% by weight of an epoxy resin or a mixture of several epoxy resins , The bondable polymer advantageously contains from 40 to 94% by weight of acrylic acid compounds and / or methacrylic acid compounds of the general formula CH 2 CC (R 1 ) (COOR 2 ) (R 1 represents a radical which is selected from the group comprising H and CH 3 , and R 2 represents a group selected from the group consisting of H and linear or branched alkyl chains having 1 to 30 carbon atoms), from 5 to 30% by weight of a first copolymerizable vinyl monomer having at least one acid group in particular a carboxylic acid group and / or sulfonic acid group and / or phosphonic acid group, from 1 to 10% by weight of a second copolymerizable vinyl monomer having at least one epoxy group or an acid anhydride function and from 0 to 20% by weight of a third copolymerizable vinyl monomer, which has at least one functional group derived from the functional group of the first copolymerizable vinyl monomer and from the functional one Group of the second copolymerizable vinyl monomer differs. Such an adhesive allows bonding with rapid activation, in which within a short time already the final bond strength is achieved, so that in total a well-adhering connection is ensured on non-polar ground.
Eine weitere einsetzbare reaktive hitzeaktiviert verklebbare Klebmasse, die besondere Vorteile bietet, enthält zu 40 bis 98 Gew.-% ein acrylathaltiges Blockcopolymer, zu 2 bis 50 Gew.-% eine Harzkomponente und zu 0 bis 10°Gew.-% eine Härterkomponente. Die Harzkomponente enthält eines oder mehrere Harze, die gewählt werden aus der Gruppe umfassend die Klebkraft steigernde (klebrig machende) Epoxidharze, Novolakharze und Phenolharze. Die Härterkomponente wird zum Vernetzen der Harze aus der Harzkomponente eingesetzt. Eine derartige Formulierung bietet infolge der starken physikalischen Vernetzung innerhalb des Polymers den besonderen Vorteil, dass sich Klebeschichten mit einer größeren Gesamtdicke erhalten lassen, ohne dass dabei die Belastbarkeit der Verklebung insgesamt beeinträchtigt wird. Dadurch sind diese Klebeschichten besonders geeignet, Unebenheiten im Untergrund auszugleichen. Überdies weist eine solche Klebmasse eine gute Alterungsbeständigkeit und ein nur geringes Ausgasungsverhalten auf, was bei vielen Verklebungen im Elektronikbereich besonders erwünscht ist. Wie bereits vorstehend erwähnt, lassen sich außer diesen besonders vorteilhaften Klebmassen jedoch grundsätzlich auch alle anderen hitzeaktiviert verklebbaren Klebmassen entsprechend dem jeweiligen Anforderungsprofil für die Verklebung auswählen und einsetzen. Another useful reactive heat-activated adhesive composition which offers particular advantages comprises from 40 to 98% by weight of an acrylate-containing block copolymer, from 2 to 50% by weight of a resin component and from 0 to 10% by weight of a hardener component. The resin component contains one or more resins selected from the group consisting of tackiness-enhancing (tackifying) epoxy resins, novolak resins, and phenolic resins. The hardener component is used to crosslink the resins from the resin component. Due to the strong physical crosslinking within the polymer, such a formulation offers the particular advantage that adhesive layers having a greater overall thickness can be obtained without impairing the load-bearing capacity of the bond as a whole. As a result, these adhesive layers are particularly suitable for compensating for unevenness in the substrate. Moreover, such an adhesive has a good resistance to aging and only low outgassing behavior, which is particularly desirable in many applications in the field of electronics. As already mentioned above, in addition to these particularly advantageous adhesives, however, it is also possible in principle to select and use all other adhesively bonded adhesives which can be heat-activated in accordance with the respective profile of requirements for the bonding.
Weiterhin vorteilhaft werden auch reaktive Haftklebstoffe, insbesondere auch solche, die sich für Strukturelles Kleben eignen, eingesetzt. Solche Klebmassen offenbaren beispielsweise die Schriften DE 199 05 800 B4 und EP 0 881 271 B1 , deren diesbezüglicher Offenbarungsgehalt in die Offenbarung dieser Schrift eingeschlossen werden soll. Reactive pressure-sensitive adhesives, in particular also those which are suitable for structural bonding, are also used to advantage. Such adhesives disclose, for example, the publications DE 199 05 800 B4 and EP 0 881 271 B1, the relevant disclosure of which is intended to be included in the disclosure of this document.
In einer vorteilhaften Ausführung der Erfindung werden beide hitzeaktivierbaren Klebmassen so ausgewählt, dass nach einer Herstellung der Verklebung durch Erwärmung des hitzeaktivierbar verklebbaren Flächenelementes durch magnetische Induktion die Verklebungsfestikeit im statischen Scherversuch auf Polycarbonat größer als 100 MPa ist, bevorzugt zwischen 100 und 300 MPa liegt und ganz besonders bevorzugt größer als 400 MPa ist. In an advantageous embodiment of the invention, both heat-activatable adhesives are selected such that after production of the bond by heating the heat-activatable bondable surface element by magnetic induction, the bond strength in the static shear test on polycarbonate is greater than 100 MPa, preferably between 100 and 300 MPa and quite more preferably greater than 400 MPa.
Vorteilhaft ist weiterhin, wenn zumindest eine der beiden, möglicherweise aber auch beide, hitzeaktivierbaren Klebmassen nur partiell beschichtet auf dem elektrisch leifähigen Flächengebilde vorliegt, etwa in Form von geometrischen Flächen (z.B. Punkten, Dreiecken, Rauten oder Hexagonen) oder linienförmigen Mustern (z.B. Stegen, Linien, Gittern oder Wellen). Dadurch kann eine weitere Differenzierung der Trennkraft auf den beiden Seiten erreicht werden. It is furthermore advantageous if at least one of the two, but possibly also both, heat-activatable adhesives is only partially coated on the electrically conductive sheet, for example in the form of geometric surfaces (eg points, triangles, diamonds or hexagons) or linear patterns (eg webs, Lines, grids or waves). This allows a further differentiation of the separation force can be achieved on the two sides.
In einer weiteren vorteilhaften Varianter der Erfindung sind die hitzeaktivierbaren Klebmassenschichten unterschiedlich dick ausgeführt. Dies hat den Vorteil, dass Klebkraftunterschiede der verschiedenartigen Klebmassen durch höhere bzw. geringere Schichtdicke ausgeglichen werden können. In a further advantageous variant of the invention, the heat-activatable adhesive layer layers are made differently thick. This has the advantage that differences in adhesive force of the various adhesives can be compensated by higher or lower layer thickness.
Elektrisch leitfähige Flächengebilde Electrically conductive sheets
Grundsätzlich kann das zumindest eine elektrisch leitende Flächengebilde beliebig geeignet ausgebildet sein, beispielsweise als dünne vollflächig-kompakte oder durchbrochene Schicht (beispielsweise als Gitter). Bevorzugt beträgt die Schichtdicke der elektrisch leitenden Schicht weniger als 50 μηη, insbesondere weniger als 20 μηη oder sogar weniger als 10 μηη. Letzteres ermöglicht es, die Aufheizgeschwindigkeit nach oben hin auf relativ einfache Weise zu begrenzen. In principle, the at least one electrically conductive sheet can be of any suitable design, for example as a thin, full-surface-compact or perforated layer (for example as a grid). The layer thickness of the electrically conductive layer is preferably less than 50 μm, in particular less than 20 μm or even less than 10 μm. The latter makes it possible to limit the heating speed upwards in a relatively simple manner.
Als induktiv erwärmbares Material des elektrisch leitfähigen Flächengebildes werden insbesondere solche insbesondere schichtförmigen Materialien gewählt, wie sie aus dem Stand der Technik an sich hierfür bekannt sind. Als elektrisch leitende Schicht wird jede Schicht aus mindestens einem Material angesehen, das bei einer Temperatur von 23 °C eine Leitfähigkeit (Elektronen und/oder Löcher) von mindestens 1 mS/m aufweist, so dass in diesem ein elektrischer Stromfluss auftreten kann. Dies sind insbesondere Metalle, Halbmetalle sowie andere metallische Materialien und gegebenenfalls auch Halbleiter, in denen der elektrische Widerstand gering ist. Damit ist der elektrische Widerstand der elektrisch leitenden Schicht also einerseits hoch genug, um beim Fließen eines elektrischen Stroms in der Schicht eine Erwärmung der Schicht zu ermöglichen, andererseits aber auch niedrig genug, um einen Stromfluss durch die Schicht überhaupt zu etablieren. Als Sonderfall sind als elektrisch leitende Schichten auch Schichten aus Materialien anzusehen, die einen niedrigen magnetischen Widerstand aufweisen (und somit eine hohe magnetische Leitfähigkeit oder magnetische Permeabilität), beispielsweise Ferrite, obgleich diese häufig einen bei Wechselstrom niedriger Frequenzen höheren elektrischen Widerstand aufweisen, so dass hier eine Erwärmung häufig erst bei tendenziell höheren Magnet- Wechselfeldfrequenzen erreicht wird. As the inductively heatable material of the electrically conductive sheet, in particular such particular layered materials are selected, as they are known from the prior art per se for this purpose. As an electrically conductive layer, each layer is considered to consist of at least one material which has a conductivity (electrons and / or holes) of at least 1 mS / m at a temperature of 23 ° C., so that an electrical current flow can occur therein. These are in particular metals, semimetals and other metallic materials and optionally also semiconductors in which the electrical resistance is low. Thus, on the one hand, the electrical resistance of the electrically conductive layer is high enough to allow the layer to flow when an electrical current flows in the layer, but on the other hand it is low enough to establish a current flow through the layer at all. As a special case are as electrically conductive layers and layers of materials to be considered, which have a low magnetic resistance (and thus a high magnetic conductivity or magnetic permeability), such as ferrites, although these often have a higher alternating current at AC low electrical resistance, so here Heating is often achieved only at a tendency to higher magnetic alternating field frequencies.
Bevorzugt werden zum Beispiel elektrisch leitfähige flächige Materialien (Flächengebilde) eingesetzt, da diese mit niedrigen Frequenzen erwärmt werden können, was eine höhere Eindringtiefe des Magnetfelds sowie geringere Anlagenkosten zur Folge hat. Bevorzugt haben diese elektrisch leitfähigen Flächengebilde eine Dicke von wenige als 50 μηη, insbesondere weniger als 20 μηη und ganz besonders weniger als 10 μηη, da die Klebebänder mit abnehmender Dicke des elektrisch leitenden Flächengebildes flexibler werden. Hiermit können besonders dünne Klebebänder zur Verfügung gestellt werden; zudem kann die Menge des auf dem einen Fügeteil verbleibenden elektrisch leitfähigen Materials vermindert werden. For example, electrically conductive planar materials (flat structures) are preferably used, since they can be heated at low frequencies, which results in a higher penetration depth of the magnetic field and lower equipment costs. Preferably, these electrically conductive sheets have a thickness of less than 50 μm, in particular less than 20 μm, and in particular less than 10 μm, since the adhesive tapes become more flexible as the thickness of the electrically conductive sheet decreases. Hereby very thin adhesive tapes can be made available; In addition, the amount of remaining on the one joining part electrically conductive material can be reduced.
In einer vorteilhaften Ausgestaltungsform weist die elektrisch leitende Schicht des hitzeaktiviert verklebbaren Flächenelements eine Schichtdicke von weniger als 20 μηη auf, insbesondere von weniger als Ι Ο μηη, um dessen Aufheizgeschwindigkeit auf besonders einfache Weise zu begrenzen. Darüber hinaus kann das Flächenelement eine weitere hitzeaktiviert verklebbare Klebmassenschicht aufweisen. Ein derartiges Flächenelement ist als zweiseitig verklebbares Flächenelement besonders geeignet, um zwei Verklebungssubstrate miteinander zu verbinden. In an advantageous embodiment, the electrically conductive layer of the heat-activated bondable surface element has a layer thickness of less than 20 μηη, in particular of less than Ο Ο μηη in order to limit its heating rate in a particularly simple manner. In addition, the surface element can have a further heat-activated adhesive layer. Such a surface element is as two-sided bondable surface element particularly suitable to connect two bonding substrates together.
Bevorzugt ist die elektrisch leitende Schicht dabei zusätzlich auch magnetisch, insbesondere ferromagnetisch oder paramagnetisch. Wenngleich für derartige Materialien erwartet wurde, dass in diesen zusätzlich zu einer Induktion von Wirbelströmen auch eine Erwärmung durch Hystereseverluste auftritt und die Erwärmungsgeschwindigkeit insgesamt größer ausfällt, so wurde hingegen beobachtet, dass selbst magnetische Materialien wie Nickel oder magnetische Stähle, die den elektrischen Strom gut leiten, durchweg geringere Erwärmungsgeschwindigkeiten haben als Materialien, die zwar den elektrischen Strom sehr gut leiten, selbst aber nicht magnetisch sind, beispielsweise Kupfer oder Aluminium. Daher lässt sich durch Verwendung von magnetischen, den elektrischen Strom leitenden Materialien die Erwärmung leichter kontrollieren und das Auftreten von Erwärmungseffekten abseits der Klebefuge vermindern. In addition, the electrically conductive layer is preferably also magnetic, in particular ferromagnetic or paramagnetic. While it has been expected for such materials that in addition to induction of eddy currents, there will also be heating due to hysteresis losses and the overall heating rate will be greater, it has been observed that even magnetic materials such as nickel or magnetic steels conduct the electrical current well have consistently lower heating rates than materials that conduct the electrical current very well, but are not themselves magnetic, such as copper or aluminum. Therefore, by using magnetic materials that conduct electricity, it is easier to control heating and reduce the occurrence of heating effects away from the bondline.
Ferner ist es günstig, wenn die elektrisch leitende Schicht eine elektrische Leitfähigkeit von mehr als 20 MS/m aufweist (was beispielsweise durch Verwendung von Aluminium erreicht werden kann), insbesondere von mehr als 40 MS/m (was beispielsweise durch Verwendung von Kupfer oder Silber erreicht werden kann), jeweils bestimmt für 300 K. Auf diese Weise lassen sich die zur Herstellung hoher Festigkeiten der Klebverbindung erforderlichen ausreichend hohen Temperaturen in der Klebefuge sowie eine homogene Durchwärmung auch in sehr dünnen Flächenelementen realisieren. Überraschenderweise wurde beobachtet, dass die Erwärmung infolge induzierter Wirbelströme mit der zunehmenden Leitfähigkeit steigt und nicht, wie erwartet, mit zunehmendem elektrischem Widerstand. Furthermore, it is advantageous if the electrically conductive layer has an electrical conductivity of more than 20 MS / m (which can be achieved for example by using aluminum), in particular more than 40 MS / m (which, for example, by using copper or silver can be achieved), each determined for 300 K. In this way, the required for the production of high strengths of the adhesive bond sufficiently high temperatures in the adhesive joint and a homogeneous heating can be realized even in very thin surface elements. Surprisingly, it has been observed that heating due to induced eddy currents increases with increasing conductivity and not, as expected, with increasing electrical resistance.
Experimenteller Teil Beispiel: Experimental part Example:
Als hitzeaktivierbare Klebmasse wurden hitzeaktivierbare Klebmassenfolien auf unterschiedlicher chemischer Basis in untersachiedlichen Dicken eingesetzt (siehe Tabelle). Hierzu konnte zum Teil auf kommerziell erhältliche hitzeaktivierbare Folien (tesa SE) zurückgegriffen werden. As heat-activatable adhesive compositions, heat-activatable adhesive films based on different chemical bases have been used in undersized thicknesses (see table). For this purpose, commercially available heat-activatable films (tesa SE) could be used in part.
Um dünnere als die kommerziell erhältlichen Klebmassendicken zu erreichen, wurden dickere Produkte in 2-Butanon aufgelöst und aus der Lösung Klebemassenschichten in der benötigten Dicke durch Ausstreichen und Trocknen hergestellt. Als elektrisch leitfähiges Flächengebilde zur Induktionserwärmung wurde eine Aluminiumfolie mit der Dicke 36 μηη verwendet. Die Metallfolie wurde beidseitig jeweils mit den Kleberschichten bei einer Temperatur von ca. 90 °C zusammenlaminiert. Dabei wird die chemische Vernetzungsreaktion noch nicht gestartet, sondern lediglich eine Haftung herbeigeführt. In order to achieve thinner than the commercially available adhesive mass thicknesses, thicker products were dissolved in 2-butanone and prepared from the solution adhesive layers in the required thickness by brushing and drying. As an electrically conductive sheet for induction heating, an aluminum foil with the thickness of 36 μηη was used. The metal foil was laminated together on both sides with the adhesive layers at a temperature of about 90 ° C. In this case, the chemical crosslinking reaction is not started yet, but only a liability brought about.
Als Verklebungssubstrate für das erfindungsgemäße Klebeband 1 wurden 2 Polycarbonatplatten 2 mit 20 mm Breite, 100 mm Länge und 3 mm Dicke verwendet, die in der Klebefuge 3 um 10 mm überlappten (vgl. Fig. 1 ). Die Verklebungsfläche umfasste hier also ein Rechteck von 10 x 20 mm Kantenlänge. Um das differentielle Trennen des Klebebands zu untersuchen, wurden die Fügepartner aus dem gleichen Material gewählt. In der Figur 1 sind weiterhin schematisch das untere Pressstempelelement 4, das obere Pressstempelelement 5 sowie die Kraft F dargestellt. As bonding substrates for the adhesive tape 1 according to the invention, 2 polycarbonate sheets 2 with a width of 20 mm, a length of 100 mm and a thickness of 3 mm were used, which overlapped in the glued joint 3 by 10 mm (see Fig. 1). The bond area included here a rectangle of 10 x 20 mm edge length. In order to investigate the differential separation of the adhesive tape, the joining partners were selected from the same material. In the figure 1, the lower punch element 4, the upper punch element 5 and the force F are also shown schematically.
Das Verklebungsverfahren wurde mit Hilfe einer modifizierten Induktionsanlage des Typs EW5F der Firma IFF GmbH, Ismaning, durchgeführt. Als Induktor zum lokalen Bereitstellen des Magnet-Wechselfeldes dient hier ein Induktionsfeldübertrager, der aus lediglich einem wassergekühlten stromdurchflossenen Leiter besteht, der als Sekundärspulenkreis eines Transformatorfeldübertragers eingesetzt wird und in einem Koaxialtransformator mit dem primärspulenseitig erzeugten Übertragerfeld in Wechselwirkung tritt. Der Induktionsfeldübertrager wurde in eine Matrix aus Polyetheretherketon (PEEK) eingebettet und die so erhaltene Anordnung als unteres Pressstempelelement 4 einer Pressvorrichtung eingesetzt, die zudem ein oberes Pressstempelelement 5 aufweist. Der Anpressdruck aufgrund der Kraft F, mit dem der Vorverbund zwischen dem unteren Pressstempelelement 4 und dem oberen Pressstempelelement 5 senkrecht zu den Seitenflächen des hitzeaktiviert verklebbaren Flächenelements beaufschlagt wurde, betrug jeweils 2 MPa. The bonding process was carried out with the aid of a modified induction installation of type EW5F from IFF GmbH, Ismaning. As an inductor for local provision of the alternating magnetic field is used here, an induction field transformer, which consists of only a water-cooled current-carrying conductor, which is used as a secondary coil circuit of a Transformatorfeldübertragers and in a coaxial transformer with the primary coil side generated transformer field interacts. The induction field transformer was embedded in a matrix of polyetheretherketone (PEEK) and the arrangement thus obtained was used as the lower compression punch element 4 of a pressing device, which also has an upper punch element 5. The contact pressure due to the force F, with which the pre-bond between the lower punch element 4 and the upper punch element 5 was acted perpendicular to the side surfaces of the heat-activated glued surface element, was in each case 2 MPa.
Mit Hilfe der modifizierten Induktionsanlage wurden für die Untersuchungen Magnet- Wechselfelder einer Frequenz von 20 kHz bei einer Pulsweite von 30 % erzeugt. Die Pulsweite gibt den prozentualen Anteil der Pulsdauer (Pulslänge) des Magnet-Wechselfelds an der Gesamtperiodendauer (der Summe aus Pulsdauer und der Dauer der Pausen zwischen zwei aufeinander folgenden Pulsen) des Magnet-Wechselfelds an. With the help of the modified induction system, magnetic fields of a frequency of 20 kHz and a pulse width of 30% were generated for the investigations. The pulse width indicates the percentage share of the pulse duration (pulse length) of the alternating magnetic field in the total period of time (the sum of the pulse duration and the duration of the pauses between two successive pulses) of the alternating magnetic field.
Die Zeit, in der das hitzeaktiviert verklebbare Flächenelement dem gepulsten Magnet- Wechselfeld ausgesetzt war (also die Dauer der induktiven Erwärmung), wurde derart eingestellt, dass die jeweils angegebenen Temperaturen erreicht wurden, und lag insbesondere in einem Bereich von 1 bis 6 s. Alle Versuche wurden zudem mit einer Nachpresszeit von 5 s durchgeführt, innerhalb derer eine induktive Nacherwärmung in einem Magnet-Wechselfeld derselben Frequenz wie beim thermischen Aktivieren der Klebemassen bei einer Pulsweite von 20 % erfolgte (entsprechend einem Verhältnis von Pulsdauer zu Pausendauer von 1 : 4). The time in which the heat-activated glued surface element was exposed to the pulsed alternating magnetic field (ie the duration of the inductive heating), was adjusted so that the respective specified temperatures were reached, and was in particular in a range of 1 to 6 s. All experiments were also carried out with a Nachpresszeit of 5 s, within which an inductive reheating in a magnetic alternating field of the same frequency as the thermal activation of the adhesives was carried out at a pulse width of 20% (corresponding to a ratio of pulse duration to pause duration of 1: 4) ,
Als Messgröße wurde die Verklebungsfestigkeit im dynamischen Zugscherversuch in Anlehnung an DIN 53283 bei 23 °C und einer Prüfgeschwindigkeit von 1 mm/min ausgewählt. Alle Versuche wurden 10 Mal wiederholt. As a parameter, the bond strength in the dynamic tensile shear test was selected on the basis of DIN 53283 at 23 ° C. and a test speed of 1 mm / min. All experiments were repeated 10 times.
Zur Lösung (Trennung) der Verklebung wurde auf die u.a. Temperaturen ohne nennenswerten Anpressdruck induktiv aufgeheizt, dann die Probestäbe der Induktionspresse entnommen und sogleich in der Wärme durch Biegung mit der Hand getrennt. To solve (separation) of the bond was on the u.a. Temperatures inductively heated without significant contact pressure, then removed the test bars of the induction press and immediately separated in the heat by bending by hand.
Folgende Tabelle zeigt die Beispiele: The following table shows the examples:
Figure imgf000026_0001
Figure imgf000026_0001
Abkürzungen: Abbreviations:
N/P. Nitrilkautschuk/Phenolharz  N / P. Nitrile rubber / phenolic resin
PA: Copolyamid  PA: copolyamide
PET: Copolyester  PET: Copolyester
SR/EP: Snthesekautschuk/Epoxidharz BeiKlebmasse Klebmasse Festigkeit Trennung spiel Seite 1 Seite 2 [MPa] auf SeitenSR / EP: Snthesekautschuk / Epoxidharz When adhesive mass adhesive strength separation game page 1 page 2 [MPa] on pages
HAF Nr. HAF Nr. Verklebungs- Lösungs- temperatur (T-i) temperatur HAF No. HAF No. Bonding Solution Temperature (T-i) Temperature
[°C] (T2) [°C] [° C] (T 2 ) [° C]
1 HAF1 HAF3 1 10 180 4 alle Seite 2 1 HAF1 HAF3 1 10 180 4 all Page 2
2 HAF2 HAF4 120 180 6 alle Seite 22 HAF2 HAF4 120 180 6 all page 2
3 HAF3 HAF4 1 15 160 7 alle Seite 13 HAF3 HAF4 1 15 160 7 all Page 1
5 HAF1 HAF5 160 300 12 alle Seite 25 HAF1 HAF5 160 300 12 all page 2
6 HAF6 HAF1 160 300 13 alle Seite 16 HAF6 HAF1 160 300 13 all Page 1
V1 HAF1 HAF1 160 300 13 3 x Seite 1 V1 HAF1 HAF1 160 300 13 3 x page 1
7 x Seite 2 bei 10 Versuchen  7 x page 2 at 10 attempts
Die Beispiele zeigen, dass mit den gewählten Kombinationen hochfeste Klebverbindungen nach dem Stand der Technik hergestellt werden können. Weiterhin trennten sich alle unterschiedlichen Klebmassenpaarungen auf der erwarteten Seite, während sich beim Vergleichsbeispiel die Seite nicht sicher vorhersagen ließ. Dies zeigt die Vorteile der erfindungsgemäßen Klebebänder auf. The examples show that with the selected combinations high-strength adhesive bonds can be prepared according to the prior art. Furthermore, all different adhesive masses separated on the expected side, while the side could not predict the safe in the comparative example. This shows the advantages of the adhesive tapes according to the invention.

Claims

Patentansprüche claims
1 . Verfahren zum Verkleben und Wiederlösen zweier Substratoberflächen, 1 . Method for bonding and redissolving two substrate surfaces,
wobei für die Verklebung ein hitzeaktiviert verklebbares Flächenelement eingesetzt wird,  wherein a heat-activated adhesive surface element is used for the bonding,
das hitzeaktiviert verklebbare Flächenelement zumindest ein elektrisch leitfähiges Flächengebilde sowie zumindest zwei Schichten unterschiedlicher hitzeaktivierbarer Klebemassen umfasst,  the heat-activated, bondable surface element comprises at least one electrically conductive fabric and at least two layers of different heat-activatable adhesives,
wobei sich die erste hitzeaktivierbare Klebmassenschicht im Wesentlichen auf der einen Seite des elektrisch leitfähigen Flächengebildes und die zweite hitzeaktivierbare Klebemasse im Wesentlichen auf der anderen Seite des elektrisch leitfähigen Flächengebildes befindet,  wherein the first heat-activatable adhesive layer is substantially on one side of the electrically conductive sheet and the second heat-activated adhesive is substantially on the other side of the electrically conductive sheet,
dadurch gekennzeichnet, dass  characterized in that
die Verklebung dadurch bewirkt wird, dass das hitzeaktiviert verklebbare Flächenelement einer Temperatur T-i ausgesetzt wird, bei der eine gleichzeitige Hitzeaktivierung der beiden hitzeaktivierbaren Klebemassen erfolgt,  the bonding is effected by subjecting the heat-activated, bondable surface element to a temperature T-i at which a simultaneous heat activation of the two heat-activatable adhesives takes place,
das Wiederlösen dadurch bewirkt wird, das die Verklebungsstelle einer Temperatur T2 ausgesetzt wird, bei der unter vorgegebenen Bedingungen lediglich eine der hitzeaktivierbaren Schichten des hitzeaktiviert verklebbaren Flächenelementes ihre Klebewirkung im Klebeverbund soweit verliert, das der Klebeverbund getrennt wird. the redissolution is effected by exposing the bonding site to a temperature T 2 at which, under given conditions, only one of the heat-activatable layers of the heat-activated bondable surface element loses its adhesive effect in the adhesive bond so far that the adhesive bond is separated.
2. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, dass 2. The method according to claim 1, characterized in that
die Temperatur T-i zur Bewirkung der Verklebung durch induktive Erwärmung des elektrisch leitfähigen Flächengebildes bewirkt wird.  the temperature T-i is effected to cause the bonding by inductive heating of the electrically conductive sheet.
3. Verfahren nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, dass die Temperatur T2 zur Bewirkung des Wiederlösens des Klebeverbundes durch induktive Erwärmung des elektrisch leitfähigen Flächengebildes bewirkt wird. 3. The method according to any one of the preceding claims, characterized in that the temperature T 2 is effected to effect the re-dissolving of the adhesive bond by inductive heating of the electrically conductive sheet.
4. Verfahren nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, dass das Wiederlösen des Klebeverbundes bei der Temperatur T2 durch ein Schmelzen oder durch Zersetzung (Dekomposition) der entsprechenden hitzeaktivierbaren Klebemassenschicht bewirkt wird. Hitzeaktiviert verklebbares Flächenelement, umfassend zumindest ein elektrisch leitfähiges Flächengebilde sowie zumindest zwei Schichten unterschiedlicher hitzeaktivierbarer Klebemassen, 4. The method according to any one of the preceding claims, characterized in that the re-dissolving of the adhesive composite at the temperature T 2 is effected by melting or by decomposition (decomposition) of the corresponding heat-activatable adhesive layer. Heat-activated adhesive surface element comprising at least one electrically conductive sheet and at least two layers of different heat-activatable adhesives,
wobei sich die erste hitzeaktivierbare Klebmassenschicht im Wesentlichen auf der einen Seite des elektrisch leitfähigen Flächengebildes und die zweite hitzeaktivierbare Klebemasse im Wesentlichen auf der anderen Seite des elektrisch leitfähigen Flächengebildes befindet, wherein the first heat-activatable adhesive layer is substantially on one side of the electrically conductive sheet and the second heat-activated adhesive is substantially on the other side of the electrically conductive sheet,
dadurch gekennzeichnet, dass die Aktivierungstemperaturen zur Erzielung der Klebeeigenschaften der hitzeaktivierbaren Klebemassen sich weniger unterscheiden als die Schmelztemperaturen der beiden hitzeaktivierbaren Klebemassen. characterized in that the activation temperatures to achieve the adhesive properties of the heat-activatable adhesives differ less than the melting temperatures of the two heat-activatable adhesives.
Hitzeaktiviert verklebbares Flächenelement, umfassend zumindest ein elektrisch leitfähiges Flächengebilde sowie zumindest zwei Schichten unterschiedlicher hitzeaktivierbarer Klebemassen, Heat-activated adhesive surface element comprising at least one electrically conductive sheet and at least two layers of different heat-activatable adhesives,
wobei sich die erste hitzeaktivierbare Klebmassenschicht im Wesentlichen auf der einen Seite des elektrisch leitfähigen Flächengebildes und die zweite hitzeaktivierbare Klebemasse im Wesentlichen auf der anderen Seite des elektrisch leitfähigen Flächengebildes befindet, wherein the first heat-activatable adhesive layer is substantially on one side of the electrically conductive sheet and the second heat-activated adhesive is substantially on the other side of the electrically conductive sheet,
dadurch gekennzeichnet, dass die Aktivierungstemperaturen zur Erzielung der Klebeeigenschaften der hitzeaktivierbaren Klebemassen sich weniger unterscheiden als die Zersetzungstemperaturen der beiden hitzeaktivierbaren Klebemassen. characterized in that the activation temperatures for achieving the adhesive properties of the heat-activatable adhesives differ less than the decomposition temperatures of the two heat-activatable adhesives.
PCT/EP2010/069041 2009-12-21 2010-12-07 Inductively heatable adhesive tape having differential detachment properties WO2011085873A1 (en)

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ES10790401.3T ES2664193T3 (en) 2009-12-21 2010-12-07 Adhesive tape that can be inductively heated with differential separation behavior
US13/517,927 US20130020022A1 (en) 2009-12-21 2010-12-07 Inductively heatable adhesive tape having differential detachment properties
MX2012006705A MX344318B (en) 2009-12-21 2010-12-07 Inductively heatable adhesive tape having differential detachment properties.
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